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.

Three European powers met with an Iranian minister to try to reopen negotiations over the limits of its nuclear activities.

Iranian and European diplomats are set to meet in Istanbul to embark on the latest drive to unpick the deadlock over Tehran’s nuclear program.