At a news conference here at the conclusion of a regional summit, Obama also downplayed recent comments from Iran's supreme leader that raised doubt in some quarters about whether negotiators could go beyond the newly announced framework agreement.
Obama suggested that Ayatollah Ali Khamenei's remarks were more about domestic politics.
Obama said there are no assurances that the U.S. and five other world powers will be able to come to a final agreement with Iran. But the president said he was "absolutely positive" that the diplomatic course he has pursued was "the best way to prevent Iran from obtaining a nuclear weapon."
"My only question is why we keep trying to short-circuit the actual negotiations. We're not disarming. We're not getting rid of our nuclear weapons. We're not giving anything up," he said.
Obama singled out recent comments from Sen.
"When you start getting to the point where you are actively communicating that the United States government and our secretary of State is somehow spinning presentations in a negotiation with a foreign power, particularly one that you say is your enemy, that's a problem," Obama said.
He also mentioned a letter Republican senators addressed to Iranian leaders on the nuclear talks.
"It needs to stop," he said.