Negotiations to resurrect the 2015 Iran nuclear deal resumed this week in Vienna, more than ten months after they first began.

Iran’s nuclear advancements in 2021 have reduced its “breakout time,” or the amount of time it would take to build a nuclear bomb.

Negotiations to resurrect the 2015 Iran nuclear deal resumed this week in Vienna, more than ten months after they began and weighed down by even more uncertainty and mutual distrust.

And time is running out. Iran’s nuclear capabilities improve with each passing week, making a return to a deal less likely. Because Washington and Tehran aren’t talking directly, US Special Envoy for Iran Rob Malley is in Austria for indirect talks mediated by European diplomats. The Biden administration believes a deal is in the works, but if no agreement is reached within the next few weeks, it may be too late.

“Our discussions with Iran have reached an impasse,” White House spokeswoman Jen Psaki told reporters on Wednesday.

“A deal that addresses the core concerns of all parties is on the horizon. However, if it is not reached in the coming weeks, Iran’s ongoing nuclear advances will make a return to the JCPOA impossible “She was referring to the formal name of the agreement, the Joint Comprehensive Plan of Action.

Former President Donald Trump’s administration unilaterally terminated the agreement in 2018, which had lifted economic sanctions on Iran in exchange for limits on its nuclear program. Tehran has made significant progress in terms of nuclear activity since then, increasing uranium enrichment and stockpiles far beyond the parameters of the 2015 agreement.

This means it has reduced its “breakout time,” or the amount of time required to build a nuclear bomb. Iran’s leaders claim the moves are in response to Trump’s re-imposition of sanctions, which have crippled the country’s economy.

In need of economic relief, Iran agreed to participate in six rounds of indirect talks resurrected by the Biden administration between April and June 2021. However, the election of hardline anti-Western cleric Ibrahim Raisi as Iran’s president in late June halted the talks until November. They have since become mired in disagreements over previous negotiations, with no significant progress made in resolving the remaining points of contention.

And, so far, those points of contention appear to be very difficult to overcome. The US wants Iran’s nuclear advances reversed, and Iran wants sanctions lifted – but both sides want the other to make the first move. And, given that the Biden administration can’t guarantee that a new agreement will be unbreakable, and given how quickly the Trump administration ripped up the original one, trust is essentially nonexistent.

“The most significant current impediment is a lack of trust, particularly on the Iranian side,” said Ryan Bohl, a Middle East and Africa analyst at Rane Risk Intelligence. This means that if a deal is to be reached, the Biden administration may have to make even more concessions to Iran.

At the same time, Iran has been flexing its muscles and signaling that it is a force to be reckoned with. On Wednesday, it unveiled a new ballistic missile as its top security official, Ali Shamkhani, stated that in the United States, “there is no coherence…to make political decisions in the direction of advancement” of the deal.

The talks also come after several weeks of drone and missile attacks on the UAE by Yemen’s Houthi rebels, who are backed by Iran. In an analyst note issued Wednesday, political risk firm Eurasia Group stated that the Biden administration “has essentially laid its cards on the table.”

Tehran’s uranium stockpiles have been enriched to near-weapons grade, and its increasingly advanced centrifuges indicate that it is approaching a point of no return, potentially rendering the original JCPOA’s non-proliferation benefits null and void.

Importantly, there is little appetite in Washington for escalation with Iran, and Biden is eager to reverse Trump’s major foreign policy legacy by resurrecting the deal. Nonetheless, continued gridlock may force the administration to reverse course and take more aggressive measures, though no details have been provided.