"We are waiting what we believe to be a definitive statement from the government of Iran, we are looking for it to come through the traditional channel," State Department spokesman Gonzalo Gallegos said.

"And then, it will be reviewed and then, we will decide where we will be going from there," he told reporters.

He was referring to a two-week deadline for Iran to give a final answer to world powers seeking a breakthrough in the crisis over the Islamic republic's nuclear program.

The offer, made by the permanent UN Security Council members -- Britain, China, France, Russia and the United States -- plus Germany, includes trade incentives and help with a civilian nuclear program in return for suspending uranium enrichment, a process which could be used to make a nuclear bomb.

The offer was officially made earlier this month by EU foreign policy chief Javier Solana, the pointman for the world powers in talks with Iran.

Ahmadinejad said in an interview aired on NBC television Monday that if the United States adopted a genuinely new approach to his country Tehran would respond in a positive way.

"Today, we see new behavior shown by the United States and the officials of the United States. My question is, is such behavior rooted in a new approach?" the president said in a rare interview with a US broadcaster.

His remarks came after the United States took the unprecedented step of sending a top diplomat -- Under Secretary of State William Burns -- to meet Iran's chief negotiator at talks in Geneva over Tehran's nuclear program.

"Ultimately we have been hearing some different things out of Iran ... what we are looking for is at the end of the two weeks, a definite statement through Solana on where the Iranians stand," Gallegos said.

US officials said they were getting confusing signals from Iran.

Ahmadinejad had announced Saturday that Iran had boosted the number of uranium-enriching centrifuges to 6,000, in an expansion of its nuclear drive that defies international calls for a freeze.

"Over the weekend, he has been talking about 6,000 centrifuges, and now all of a sudden there is almost a conciliatory tone in his comments. I think ultimately part of the issue is we are looking for a consistent, clear message from them," a senior State Department official said, speaking on condition of anonymity.

The two week deadline expires on Saturday.

Iran already faces three sets of UN Security Council sanctions over its refusal to halt uranium enrichment, and the United States has warned Tehran of "punitive measures" if it spurns the offer and presses on with enrichment..

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