Washington, Feb 12 - The US administration doesn't believe Iran has the capacity to produce high-grade uranium with a purity of 20 percent, White House spokesman Robert Gibbs said.
"We do not believe they have the capacity to enrich to the degree to which they say they are now enriching," Gibbs said during a media briefing Thursday, noting Iran's nuclear programme "has undergone a series of problems throughout the year".
He added Iran's statements are "based on politics, not on physics".
On Thursday, Iranian President Mahmoud Ahmadinejad said his country has succeeded in producing enriched uranium fuel with 20 percent purity.
He made the announcement to mark the 31st anniversary of Islamic Revolution that ended the pro-American Shah Mohammad Reza Pahlavi's regime in 1979, Xinhua reported.
US President Barack Obama threatened to develop "a significant regime of sanctions" over the next several weeks targeting Iran.
On Wednesday, the US Treasury Department slapped new sanctions against the Iranian Revolutionary Guard Corps, freezing assets of an individual and four companies affiliated with it.
Iran has been at the centre of an international dispute over its nuclear plan. The US and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of a civilian programme.
Iran has stressed its nuclear programme is for peaceful civilian energy purposes. (IANS)