The clash over Iran's nuclear program is escalating, with U.S. sanctions and Europe's snapback threat putting Tehran under maximum pressure.

Iran has long insisted its program is peaceful, though it is the only non-nuclear-armed nation enriching uranium at that level. The U.S., the IAEA and others say Iran had a nuclear weapons program up until 2003.

Iran will meet next week with Britain, France and Germany for talks on its nuclear programme, the parties said Friday, as the European powers warned Tehran to engage swiftly to avoid snapback sanctions.