The United States on Thursday urged Iran to comply with a UN Security Council resolution that requests Iran to suspend uranium enrichment and warned of action if Iran fails to comply.

"There is still time before August 31 for Iran to comply. We encourage Iran to make the right choice," State Department acting spokesman Gonzalo Gallegos said at a briefing.

"We are looking at the August 31 date and once we get there we'll begin to take action. We are working with the UN Security Council to do this in an expedited manner," Gallegos said.

The United States said on Wednesday that Iran's response to a package of incentives put forward by the six major nations fell short of the conditions of the UN Security Council resolution.

"The response however, falls short of the conditions set by the Security Council, which require the full and verifiable suspension of all enrichment-related and reprocessing activities," Gallegos said in a statement.

Iran gave its response to the incentives package on Tuesday, but refused to suspend uranium enrichment, a key demand by the U.S. and the West.

The U.S. has accused Iran of trying to develop nuclear weapons under the cover of civilian nuclear programs. Iran has said its nuclear programs are for peaceful purposes only.