Iran's expanding missile and drone program, along with its increased weapon transfers to Russia, are hardening the U.S. position in nuclear negotiations to the point where restoring the 2015 nuclear deal (or reaching any successor agreement) may become politically infeasible — raising the risk of an Iran-U.S. nuclear crisis and potential military confrontation. In recent weeks, Iran has made announcements highlighting the acceleration of its nuclear and missile programs, both of which concern Western governments and show that the United States' strategy of separating Iran's nuclear program from the rest of its national security agenda is becoming increasingly untenable. On Nov. 10, the head of the Islamic Revolutionary Guard Corps' aerospace unit said Iran had successfully developed hypersonic missiles — which theoretically could carry a nuclear warhead — and claimed the missile would be able to ''breach all the systems of anti-missile defense.'' On Nov. 22, the International Atomic Energy Agency said that Iran had begun enriching uranium to 60% at its Fordow Fuel Enrichment Plant and that Tehran intended to install 14 cascades of its advanced IR-6 centrifuges. Iran has also been sending missiles and drones to Russian troops fighting in Ukraine, causing further alarm in the United States and Europe.

• Iran appears to be developing a hypersonic glide vehicle (HGV), which is a warhead that can fly at hypersonic speeds and remain maneuverable. This makes them far more difficult to counter compared with ballistic missiles, which follow a specific path. 
• Prior to enriching uranium to 60% at Fordow, Iran had only been enriching uranium to 60% at its Natanz plant. Fordow is an underground facility, making it more difficult for Israel or the United States to attack and destroy. 
• White House National Security Council spokesman John Kirby said on Dec. 9 that Iran and Russia had seen ''an unprecedented level of military and technical support that is transforming their relationship into a full-fledged defense partnership,'' citing both Iranian-Russian plans to jointly manufacture drones in Russia and Russia training Iranian pilots to fly Russian Sukhoi Su-35 fighters. 

Iran has aggressively advanced and deployed its drone and missile programs since the United States left the 2015 Joint Comprehensive Plan of Action (JCPOA) in 2018. Ballistic and cruise missile (and more recently drone) technologies have long been a crucial component of Iran's national security strategy. And in recent years, the importance of these weapons to Iran's national security agenda has only grown. Iran's missile and drone programs enable it to project force beyond its border and compensate for shortcomings in Iran's conventional air force and army. Iran also needs to develop its ballistic and now hypersonic missile capabilities in case it decides to develop nuclear weapons, because in order to have the reliable deterrent that nuclear weapons provide, Iran would need to have a delivery system. Moreover, Iran's drone and missile programs are critical in increasing the military capacity of the various foreign militias Tehran supports in the region (like Houthi rebels in Yemen) against better-equipped adversaries.

• Iran's air force and army largely still depend on old Western systems sold to the country before its 1979 Islamic Revolution. Iran's air force, for example, is heavily reliant on F-4 and F-14 fighters developed over 50 years ago. 
• Iran has repeatedly demonstrated its willingness to deploy its arsenal of ballistic and cruise missiles against U.S. and Israeli interests, including the January 2020 attack on an Iraqi air base hosting U.S. troops and the March 2021 attack on an Israeli ship in the Arabian Sea. Iran's drones (and missiles) have also been used either directly or indirectly to target Saudi Arabia and the United Arab Emirates, including the 2019 attack claimed by Yemen's Houthi rebels on Saudi Arabia's Abqaiq oil processing facility (which is arguably the world's most important oil facility, with a processing capacity of about 7 million barrels per day, or roughly 7% of the global oil supply). 

The United States is becoming increasingly concerned about Iran's drone and missile program and the broad threat it could pose to U.S. interests in the Middle East and elsewhere, given Tehran's demonstrated willingness to not only use such weapons but provide them to other countries like Russia. Prior to 2015, the United States' primary concern with Iran beyond its nuclear program was Tehran's financial, logistical and small arms support of militias and terrorist groups carrying out physical attacks against U.S. troops in the Middle East and U.S. regional partners, such as Israel. Washington has always been concerned about Iran's missile development — particularly ballistic missiles that could be used in a fully functional nuclear weapon. But Tehran's increased use of drones and missiles (coupled with the U.S. drawdown of troops in the Middle East) over the past five years has pushed it up on Washington's list of priorities. Moreover, Iran's transfer of weapons to Russia has been a significant focal point in the United States this year, with the U.S. Pentagon and State Department both making several public announcements about Iran sending weapons to Russia and Russia training Iranian pilots. For Washington, Iran's recent arms exports to Russia demonstrate that Tehran's drone and missile program, which had once predominantly been a concern about regional stability, could have broader implications. And this emerging reality is making it more difficult for the United States to segment Iran's ballistic and drone programs from Iran's nuclear program in its talks with Iran, given that the former is now clearly having a much more significant impact on Washington's primary interest: the ongoing war in Ukraine.

• On Nov. 14, the U.S. State Department's Iran envoy said the United States was not pushing for renewed nuclear talks with Iran due to Tehran's recent drone sales to Russia, as well as the Iranian government's heavy-handed domestic crackdown on ongoing protests over the death of a young woman in police custody. 
• On Oct. 17, a U.S. State Department official said Iran was violating a U.N. Security Council resolution by sending drones to Russia for use in Ukraine. 

But Iran's nuclear program remains a critical part of its national security and one the United States cannot overlook, as Iran's nuclear breakout time is likely down to just a few months. Despite ostensibly saying it has no nuclear weapon ambitions, Tehran appears to be trying to gain as much of the technological capabilities needed to build a nuclear weapon and enrich uranium to 90%, or weapons-grade. Since the JCPOA broke down in 2018, Iran has enriched uranium to 60% — well above the 20% threshold generally considered the top end of enrichment needed for most civilian applications. Iran has also started efforts to produce uranium metal, which Western diplomats say has no civilian use. Iran has begun researching and installing more advanced and efficient centrifuges as well, which could enable Tehran to more rapidly enrich uranium to weapons grade if wanted. Even if Iran agrees to dismantle these centrifuges in the future as part of a new deal, the know-how it's currently developing would still reduce the country's nuclear breakout time in the future. But Iran also uses the threat of its nuclear program to draw Western attention away from other issues, including its missile and drone strategy. By having a provocative nuclear program, Iran hopes to narrow the scope of any talks with the West over sanctions relief to the nuclear issue, which is likely of less importance to Tehran than its other activities. Washington's growing attention on Iran's transfer of drones and missiles to Russia is thus only granting Tehran a greater incentive to escalate the nuclear issue further.

• Iran's enrichment to 60% is of particular concern to the West as there is very little work (measured in separative work units used to measure the amount of effort needed to enrich uranium to a certain level) to enrich uranium to 90% once it is already enriched to 60%.

While Washington is currently focusing more on Iran's growing defense relationship with Russia, an Iran-U.S. nuclear crisis is probably bubbling under the surface, as negotiations remain stalled and the JCPOA likely no longer adequately addresses U.S. concerns. The JCPOA is technically in force despite the U.S. withdrawal and Iran suspending its compliance, which means that many of its sunset clauses are starting to go into effect. One of the key sunset clauses that expire in October 2023 is the U.N. ban on the transfer of ballistic missile technology to and from Iran (i.e. Iran's sales of missiles to Russia). Under the deal, the United States is also supposed to remove (and not just suspend the application of) sanctions on Iran in October. Washington wants none of these sunsets to occur, making a simple re-entry into the JCPOA difficult. Moreover, from a proliferation standpoint, the technical conditions prior to the signing of the JCPOA have changed because Iran has more advanced centrifuges, has enriched uranium to higher levels and has seen Washington exit the deal before — something that Tehran will be more concerned about as the 2024 U.S. election approaches, which yield a new White House administration. These make some of the technical conditions that the JCPOA has included more difficult to revert to. There may still be a brief window to revive the JCPOA (and largely ignore some of the sunset clauses) during the first few months of 2023, before the October deadline for those clauses to take effect start looming ever larger over negotiations. But the United States is unlikely to seize that window due to its growing concerns with Tehran's missile and drone programs and weapon transfers to Russia. The embattled 2015 deal is thus highly unlikely to be restored and more likely to become, at best, a blueprint to start from in drafting up a new Iran-U.S. nuclear agreement. 

The United States has no good diplomatic options to address Iran's growing nuclear and non-nuclear activities, and its focus on the Ukraine war and Iran's role in it is likely to ensure that diplomacy fails to reach a new agreement. There are two main diplomatic options the United States can pursue beyond the JCPOA, but neither is good. First, the United States could try to use the 2015 nuclear deal as a starting point to negotiate another broad deal where it would offer similar sanctions relief in exchange for similar restrictions on Iran's nuclear program. The White House may try to include Iran's missile and drone program in talks, but Tehran has repeatedly ruled out such inclusion and will likely continue to do so. There is virtually no trust between Washington and Tehran, and Tehran won't agree to similar conditions on its nuclear program without substantial guarantees from Washington that it won't exit the deal. In order for this option to actually yield an agreement, the United States might have to settle for fewer restrictions on Iran's nuclear program, making it more difficult to sell at home. But such an agreement would also allow Iran to save face and say it gained concessions from the United States. The United States' other option is pursuing a limited agreement with Iran similar to the 2012 Joint Plan of Action that preceded the JCPOA. In such an arrangement, Washington would try to freeze Iran's nuclear activities at current levels or at levels significantly higher than the 2015 JCPOA (such as at 20% enrichment). The United States would only offer limited sanctions relief in exchange for placing a cap on Iran's nuclear program. While this may provide a temporary fix from Washington's perspective, it wouldn't necessarily reduce Iran's breakout time significantly. The United States also proposed such a limited agreement as an interim deal in 2021, which Iran quickly rejected. A narrow agreement, however, would allow the U.S. to tie broader sanctions relief to non-nuclear issues in addition to nuclear issues in the future. 

Should diplomatic efforts fail, the United States will face increased calls from Iran hawks both at home and in Israel to escalate against Iran, potentially even militarily. With Iran's nuclear breakout time probably at no more than six months, Iran hawks in Israel and the United States will likely propose covert and overt options to disrupt and push back Iran's nuclear program, even if temporarily. The Biden administration will likely try to keep the Iran nuclear issue on the back burner to maintain its focus on the Ukraine war, but Iran's nuclear advancement may make this impossible. There remain several triggers that could lead to more aggressive U.S. action, including Iran announcing it will enrich uranium to 90%, Iran rejecting IAEA inspections under the Additional Protocol, Iran withdrawing from the Non-Proliferation Treaty, and Iran announcing more advancements in uranium metal production. In Israel, former Israeli Prime Minister Benjamin Netanyahu's expected return to office will also likely lead to an even more hawkish position and call for strikes on Iran. Even if Biden avoids those calls during his presidency, military escalation in the future under a different administration — potentially as early as 2025, if the Republicans gain the White House — will become more likely.