The United States said Wednesday that Iran was moving closer to being able to produce a nuclear bomb by stockpiling enriched uranium and, along with European allies, urged Tehran to engage in talks over its atomic program.

"Iran is now either very near or in possession already of sufficient low-enriched uranium to produce one nuclear weapon if the decision were made to further enrich it to weapons-grade," Glyn Davies, Washington's chief envoy to the International Atomic Energy Agency said. "This ongoing enrichment activity ... moves Iran closer to a dangerous and destabilizing possible breakout capacity," he said.

The latest agency report says Iran now has, at a minimum, 3,153 pounds of low-enriched uranium hexafluoride, he added.

"Taken in connection with Iran's refusal to engage with the IAEA regarding its past nuclear warhead-related work, we have serious concerns that Iran is deliberately attempting, at a minimum, to preserve a nuclear weapons option," Davies told a meeting of the U.N. nuclear watchdog's 35-nation governing board.