France, Germany and the United Kingdom have written to United Nations Secretary-General António Guterres and the Security Council warning that they are prepared to trigger the JCPOA “snapback” mechanism and reinstate UN sanctions on Iran unless Tehran resumes nuclear negotiations and restarts cooperation with International Atomic Energy Agency inspectors before the end of August 2025, according to a letter seen by the Financial Times and cited by multiple media outlets, including Reuters and the BBC. The three European powers—known as the E3—say Iran has halted collaboration with the IAEA and amassed a uranium stockpile more than 40 times the limit set under the 2015 nuclear accord. While the E3 stress their commitment to a diplomatic resolution, they argue that Iran’s continued non-compliance constitutes “significant non-performance” that legally justifies a reimposition of all UN restrictions lifted in 2015. They have indicated that sanctions could be delayed until mid-September if Tehran promptly returns to talks and grants inspectors access. The ultimatum comes two months after U.S. and Israeli strikes on Iranian nuclear facilities derailed earlier negotiations and heightened regional tensions. Iranian lawmakers have threatened to withdraw from the Nuclear Non-Proliferation Treaty if sanctions are reinstated, underscoring the high stakes of the E3’s warning. For now, European diplomats say the door to diplomacy remains open, but failure to act by the August deadline will pave the way for a comprehensive re-imposition of global arms, banking and energy sanctions on Iran.