Time is running out for Iran to avoid sanctions over its nuclear program, Reuters quoted White House spokesman Robert Gibbs as saying on Thursday. He added that Teheran's deadline is still the end of the year for responding to international demands.
Iran has ignored a deal offered by the Western powers that would have Iran sending its low-enriched uranium abroad for processing into uranium for making fuel. Reuters quoted Gibbs as saying it was "pretty clear" that the Iranians were backing out of that agreement.
The White House comments came a day after Iranian President Mahmoud Ahmadinejad declared that his country will enrich uranium to a much higher level - a fresh rejection of an international plan to curb Teheran's nuclear program.
"I declare here that with the grace of God, the Iranian nation will produce 20 percent fuel and anything it needs itself," Ahmadinejad told a cheering crowd in the central city of Isfahan on Wednesday.
Iran denies any interest in developing nuclear arms, and Ahmadinejad's speech made no suggestion the Islamic republic was planning to turn its enriched uranium stockpile into material that could be used in nuclear warheads.
Ahmadinejad said Teheran was ready to further enrich some of its present stockpile - now at 3.5 percent - to 20 percent, the grade needed to create fuel for a small medical research reactor in the Iranian capital.
In related news, Iranian nuclear negotiator Saeed Jalili met with Hamas leaders on Thursday during a visit to Syria.
The group's deputy political leader, Moussa Abu Marzouk, said they discussed Palestinian affairs, without providing any further details.