El-Baradei told Germany's "Der Spiegel" news magazine that European diplomatic efforts can only be successful if Washington joins the talks.
The United States has accused Iran of pursuing a nuclear-weapons program -- a charge Tehran vigorously denies.
France, Britain, and Germany have sought to persuade Iran to scrap any nuclear-weapon-related activities in return for economic incentives. The United States has not been directly involved in that diplomatic effort.
In an interview with Belgian television broadcast late yesterday, U.S. President George W. Bush said he wanted diplomacy to work in the dispute with Iran.
"We've [the United States and Europe] got a common goal, and that is that Iran should not have a nuclear weapon," Bush said. "That's what we have said, that's what the Brits have said, the French have said, the Germans have said, when they send their foreign ministers into talk to the Iranians. There's a common mission, and I look forward to making sure we continue to speak with one voice."
Russian President Vladimir Putin said yesterday that Russia would continue assisting Iran in developing a nuclear-energy program, adding that Moscow does not believe
that Tehran is covertly seeking to develop nuclear weapons.