The United States admitted yesterday that promoting sanctions against Iran over its suspect nuclear program is a tough job which might take weeks before it is done.

Due to tough resistance from some member states of the UN Security Council, the process of trying to hammer out a sanctions package in the Security Council "would take weeks", State Department spokesman Sean McCormack said at a news briefing.

"The reality of it is that there are going to be intense negotiations on this," he said.

The latest U.S. official estimation is apparently behind ambitious timetable put forward earlier by Undersecretary of State Nicholas Burns, who said a deal would be reached in September.

However, the spokesman said, "Our diplomatic interactions indicate that while this will be complex, sometimes hard-fought diplomacy, that we will, in fact, end up with a Security Council resolution that includes sanctions."

Washington has been expecting the sanctions to be imposed in a graduated manner to build pressure on Iran to give up its enrichment program and accept international offers to help it develop a monitored civilian nuclear power industry.

U.S. Secretary of State Condoleezza Rice confirmed Wednesday that she will meet her fellow foreign ministers from the permanent Security Council members plus Germany on the sidelines of the General Assembly meeting in New York to discuss the sanctions.