Iranian and European delegations are expected to gather in Istanbul, Turkey, on Friday for fresh talks on Tehran's nuclear program, with European nations warning that a failure of negotiations may prompt punishing "snapback" sanctions on Iran.

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

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.