Describing Iran as a "threat" to America's national security, a top Pentagon official has told the lawmakers that the US is determined to prevent Tehran from acquiring nuclear weapons.
"Iran is a threat to US national security in many ways, not simply their move toward the potential to develop a nuclear weapon," chairman of the joint chiefs of staff General Martin Dempsey said during a Congressional hearing on Wednesday.
"I choose my words carefully, because the intelligence community has not yet come to a conclusion that they intend to build a nuclear weapon, but they're certainly preserving and building on their options to do so, which should be of concern to all of us and is," he said in response to a question.
"We have been very clear as a nation that we are determined to prevent them from acquiring a nuclear weapon because it would be so destabilising to the region. But they are also active in cyber.
"They've got surrogates all over the region and all over the world. They proliferate arms. They are a disruptive influence globally. And so I do consider them a threat to our national security," Dempsey said.
Defence secretary Chuck Hagel said the US remains focused on preventing Iran from acquiring nuclear weapons.
"It's certainly giving them options to move in that direction," he said when senator Lindsay Graham asked: "Do you think what they're doing with the centrifuges is designed to produce weapons material or just peaceful power?"
The US and other Western powers accuse Iran of covertly carrying out nuclear activities to develop atomic weapons, a charge denied by Tehran.