Time is running out for Iran to avoid sanctions over its nuclear program, a White House spokesperson said on Thursday, and Tehran's deadline is still the end of the year for responding to international demands.

"Time is running out. That deadline is the end of the year," White House spokesperson Robert Gibbs told reporters in a news briefing.

Iran has resisted a deal with Western powers that would see its low-enriched uranium sent abroad for processing into uranium for making fuel. Gibbs said it was "pretty clear" that the Iranians were backing out of that agreement.

Washington and its allies suspect Iran is secretly using its nuclear energy program to develop nuclear weapons, but Tehran says it is enriching uranium only to generate electricity.

-Reuters/NOW Lebanon