The White House said Thursday the U.S. administration doesn't believe Iran has the capacity to produce high-grade uranium with a purity of 20 percent, suggesting Tehran is making exaggerated claims for political reasons.

"We do not believe they have the capacity to enrich to the degree to which they say they are now enriching," White House Spokesman Robert Gibbs said during a regular briefing, noting Iran 's nuclear program "has undergone a series of problems throughout the year."

He also charged that Iran's statements are "based on politics, not on physics."

Iranian President Mahmoud Ahmadinejad announced earlier Thursday his country's production of the first batch of high grade uranium, saying that "the first batch of 20 percent (enriched uranium) fuel was produced."

"Right now in Natanz, we have the capability to enrich 20 percent and 80 percent (uranium), but since we don't need it, we don't enrich (to the higher grade)," Ahmadinejad said.

Ahmadinejad made the announcement to mark the 31st anniversary of Islamic Revolution which ended the pro-American shah regime in 1979. On Tuesday, Iran just announced it began enriching uranium to a level of 20 percent at its Natanz enrichment facility.

U.S. President Barack Obama threatened to develop "a significant regime of sanctions" over the next several weeks targeting Iran, and on Wednesday, the Treasury Department slapped further sanctions against Iranian Revolutionary Guard Corps, freezing assets of an individual and four companies affiliated with it.

Iran has been at the center of an international dispute over its nuclear plan. The United States and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of a civilian program.

Iran has denied the accusation and stressed its nuclear program is only for peaceful purposes.