The U.S. wants Iran to end all uranium enrichment. The European nations have yet to make clear their position. The JCPOA limited Iran to enriching uranium up to 3.67% purity -- sufficient for civilian nuclear power purposes but below the 90% purity needed for use in a weapon.

President Donald Trump warned on Monday that he would order fresh U.S. attacks on Iran's nuclear facilities should Tehran try to restart facilities that the United States bombed last month.