The consequences of Iran acquiring a nuclear weapon would be "calamitous" and major powers must act together to prevent it, the top U.S. military officer said on Thursday.

Admiral Mike Mullen''s remarks came the day after Iran''s president announced the country had tested a missile that analysts said could hit Israel and U.S. bases in the Gulf, a major source of crude oil for the United States.

The United States and other Western powers are concerned that Iran could combine elements of its uranium enrichment and missile programs to create a nuclear weapon, although Tehran denies it intends to do this.

"I''m one who believes that Iran getting a nuclear weapon is calamitous for the region and for the world," Mullen, chairman of the U.S. Joint Chiefs of Staff, told the U.S. Senate Foreign Relations Committee.

"It then, in my view, generates neighbors who feel exposed, deficient and then develop or buy the capability themselves," he said, suggesting Iran''s acquisition of a nuclear weapon likely would trigger a nuclear arms race in the Middle East.

"The downside, potentially, is absolutely disastrous."

But Mullen did not suggest the United States should take military action to prevent Iran from acquiring nuclear weapons.