Washington, Apr 15 (DPA): The US is pursuing UN Security Council sanctions on Iran with a "sense of urgency" for its continued defiance of international demands to come clean about its nuclear activities, a senior US official has said.

"What we seek is the strongest possible sanctions resolution in the short possible time," Bill Burns, undersecretary of state, said Wednesday, referring to President Barack Obama's goal of getting the council to adopt the measures this spring.

Burns and other top defence and intelligence officials testified before a Senate committee on Iran ahead of a meeting in New York later Wednesday between representatives from the the five permanent members of the Security Council - Britain, China, France, Russia and the US - plus Germany.

The powers are to meet to discuss a resolution and as Obama appears to have won some support from holdouts China and Russia. Obama met with Chinese President Hu Jintao Monday on the sidelines of a nuclear summit in Washington.

Iran has already faced three sanctions resolutions in recent years over suspicions it is using a civilian nuclear programme as a guise for pursuing weapons. Iran rejects the allegations.

Meanwhile, General James Cartwright, the vice chairman of the Joint Chiefs of Staff, said Iran could possibly have enough enriched uranium within a year to build a bomb, but it would take several years after that to have a usable weapon.

"It would take another two to three, potentially out to five years, to move from the idea of having the material to a deliverable weapon that is usable," he told the senators.