The United States gave a cool reception Tuesday to a mooted deal between the IAEA and Iran, saying the agreement marked a "step forward" but stating that Tehran would be judged on its actions.
International Atomic Energy Agency chief Yukiya Amano said upon returning from Tehran that he and Iran's chief nuclear negotiator made a "decision" to reach an agreement on the UN watchdog probing suspected weapons activities.
But contrary to the hopes of some diplomats before he left on Sunday, Amano failed to actually sign a deal, saying at a Vienna airport that this would happen "quite soon" because of remaining, unspecified "differences."
"It's important to note that the announcement today is a step forward," White House spokesman Jay Carney said, calling the planned agreement "certainly significant."
However, he added: "We will make judgments about Iran's behavior based on actions."
State Department spokeswoman Victoria Nuland also stressed that "the announcement of the deal is one thing, but the implementation is what we're going to be looking for" ahead of talks Wednesday in Baghdad between Iran and six world powers including the United States.
Washington will look for Iran to "provide the access to all of the locations, the documents and the personnel that the IAEA requires in order to determine whether Iran's program is exclusively for peaceful purposes," she said.
The Baghdad talks, aimed at defusing the crisis over Tehran's contested nuclear program, involve Iran and the five permanent members of the UN Security Council -- Britain, China, France, Russia and the United States -- plus Germany.
"We see these issues in parallel," Nuland said of the IAEA's work and the talks in the Iraqi capital.
"We are looking for Iran to demonstrate unequivocally that its program is peaceful. So there are separate, but linked tracks for doing that.
"One is to do what the IAEA needs to demonstrate that it has seen all the locations, all the documents. And the other is to work with the EU 3-plus-3 on concrete steps to give more reassurance of the kind that we're seeking," she said.
Republican Representative Ileana Ros-Lehtinen, who has pressed for tighter sanctions on the Islamic republic, called the apparent deal a "stalling tactic" to give Tehran more time to acquire nuclear capability.
A key demand of world powers is that Iran address accusations in a major IAEA report in November that, until 2003, and possibly since, Tehran did work "relevant to the development of a nuclear explosive device."
One Western diplomat told AFP there had been "no breakthrough" in Amano's visit. Another said the trip appeared disappointing but that they were waiting for a "clearer picture" at meetings in Vienna later on Tuesday.
"This is only a promise, and Iran has made many, many promises in the past," said a third diplomat, adding that Tehran was possibly trying to appear cooperative ahead of the meeting in Baghdad.
The US mission in Vienna said that while it appreciated Amano's efforts, it was "concerned by the urgent obligation for Iran to take concrete steps to cooperate fully" with the agency.