European and Iranian diplomats have arrived in Istanbul in a renewed effort to resolve the standoff over Tehran's nuclear program. The talks mark the first formal engagement since June's 12-day war between Iran and Israel, a conflict that included U.S. airstrikes on Iranian nuclear facilities and heightened tensions across the region.

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

The so-called E3 - Britain, France and Germany - have warned they will invoke the United Nations snapback mechanism to reimpose international sanctions on the Islamic Republic.