Six world powers and Iran are meeting in the Turkish city of Istanbul for talks aimed at ending the deadlock over Tehran's nuclear programme.
Envoys from the US, UK, France, China, Russia and Germany hope the talks will halt rising regional tension.
Iran says its nuclear programme is peaceful, but critics suspect it of seeking to develop nuclear weapons.
Israel has hinted in recent months that it could carry out a pre-emptive strike on Iran to prevent that happening.
The talks are the first to be held between Iran and the world's major powers for 15 months.