Washington: The US said on Wednesday it was waiting for clearer signs from Iran that it was serious about taking up an offer by the international community to exchange nuclear fuel.
Defence Secretary Robert Gates said the US was looking at a "full range of options" and would consider additional sanctions if Iran pushed forward with a suspected nuclear weapons programme.
Iranian President Mahmoud Ahmadinejad said on Tuesday that Iran was ready to ship its low-enriched uranium out of the country, in exchange for a more highly processed version to be used as fuel in a medical-purpose reactor in Tehran.
The apparent shift was met with caution by the international community, which urged Iran to inform the Vienna-based International Atomic Energy Agency (IAEA) of its readiness to accept the deal. The West believes Tehran is seeking nuclear weapons, which Iran denies.
If Iran continues to pursue nuclear weapon technology, Gates said there were "more likely to be severe sanctions imposed partly by the UN Security Council and partly by the US and like-minded countries."
US State Department spokesman PJ Crowley said the US was still seeking "clarification" on Iran`s new position.
"I think from our standpoint, we will look for actions as opposed to just words," Crowley said, but added that an official acceptance of the deal would be welcomed.
"If, as (Ahmadinejad) suggested, Iran is willing to move forward to accept the arrangement that has been offered ... this would be of benefit to the ... Iranian people, and it would clearly be welcome news, you know, for the international community," Crowley said.
The US also rejected Ahmadinejad`s offer of releasing three American hikers held in Iran in exchange for Iranian citizens held in US prisons.