WASHINGTON: Senior Obama administration officials said on Thursday they were struck by the number of significant technical problems Iran appears to be encountering on the road to a nuclear weapon.

The US officials, briefing reporters on a new International Atomic Energy Agency report, said Teheran is showing more evidence of trying to move toward a nuclear weapons capability but may be running out of uranium.

"The fact that they have increased the level of non-cooperation indicates to me that unless we can mount the international pressure to stop it, this program is heading more and more in the direction of seeking a weapons capability," one official said.