United Nations nuclear watchdog experts will visit Tehran Wednesday with hopes of furthering their investigation into Iran's controversial nuclear program.

Officials from the International Atomic Energy Agency said they hope to address what the IAEA calls “overall, credible” evidence of nuclear weapons research work.

The IAEA and the West are concerned Iran is in stages of possibly developing a nuclear weapon. Iran says its nuclear ambitions are peaceful.

Iranian Foreign Ministry spokesman Ramin Mehmanparast said Tuesday that a religious decree issued by Iran's supreme leader banning nuclear weapons is binding for the Iranian government.

IAEA representatives have been blocked by the Iranian government from visiting key nuclear sites. The IAEA and Tehran continue to negotiate over possible access.

The visit comes as international diplomats are again setting the stage for separate negotiations with Tehran over curbs to its nuclear ambitions.

With Israel threatening military action against Iran, Iranian diplomats and the so-called P5+1 contact group – the United States, Britain, Russia, China, France and Germany – are expected to try to open talks in the coming weeks after a seven-month hiatus.

The last time Iran's nuclear negotiators met with their foreign counterparts, in Moscow in June, the talks did not go well. Both sides wanted their maximum demands met, and offered little in return.