The European Union and Iran resumed high-stakes negotiations in Doha on Thursday, with discussions focused on Tehran’s nuclear program and the looming threat of renewed international sanctions.

EU foreign policy chief Kaja Kallas met Iranian Foreign Minister Abbas Araghchi in an effort to find a diplomatic solution. The talks followed a one-month ultimatum issued last week by Britain, France, and Germany—known as the E3—urging Tehran to cooperate or risk the so-called “snapback” of sanctions suspended under the 2015 nuclear deal.

An EU official said the discussions centered on key issues, including the International Atomic Energy Agency’s access to Iranian facilities and the future of Iran’s stockpiles of highly enriched uranium.

The 2015 agreement, signed by Iran, the U.S., the E3, Russia, and China, offered sanctions relief in exchange for curbs on Iran’s nuclear activities. However, the deal unraveled after the U.S. withdrew in 2018 under President Donald Trump, reinstating sanctions and imposing new ones.

Since then, Tehran has steadily reduced compliance, expanding uranium enrichment in defiance of the accord. Western governments and Israel accuse Iran of seeking to build nuclear weapons, while Iran insists its program is for civilian energy purposes and asserts its right to develop nuclear technology.