The chief United Nations nuclear inspector says no deal has been reached with Iran to investigate that nation's controversial nuclear program, but that a meeting will take place next month on the issue.

International Atomic Energy Agency team leader Herman Nackaerts said Friday that two days of “intensive discussions” in Tehran failed to produce an agreement on access to Iranian nuclear facilities.

Citing unspecified “differences,” Nackaerts said the two sides could not agree on a structured approach to resolve outstanding issues. He said another round of talks will take place February 12 in Tehran.

The IAEA had hoped to gain access to the Parchin military site, which Western nations suspect is related to nuclear weapons development. Iran says it is a conventional military site and that its nuclear program is strictly for peaceful purposes.

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

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

Iran 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 they offered little in return.