He called it an opportunity to help defuse the collision over Iran’s nuclear program, but added it remains to be seen if that will turn out to be the case.

“I see it as a potentially hopeful sign. I think the question for us now is, if he is interested in, as he has said in his campaign events, mending . . . Iran's relations with the rest of the world, there's an opportunity to do that,” he said on the CBS program “Face the Nation.”

“If he lives up to his obligations under the U.N. Security Council resolutions to come clean on this illicit nuclear program, he will find a partner in us, and there will be an opportunity for that,” McDonough added.

The White House on Saturday congratulated Iranians for their “courage” after Rouhani was elected in an upset.

McDonough reiterated those views Sunday.

“Notwithstanding the very difficult circumstances the Iranian people went to the polls under lack of press freedom, lack of transparency, harassment in many cases, I think we should all be quite proud of the way that Iranians turned out to vote and to express their democratic views and aspirations,” he said.