First, under the Clinton administration, some countries demanded that fissile-materials negotiations include formal talks on nuclear disarmament and a ban on weapons in space.

WSJ: U.S. and Russia Push Arms-Control Talks Forward

Mr. Obama said the two "emphasized our shared approach" to Iran, and agreed there is still "time and space" for diplomacy to work in curbing the country's nuclear program, the subject of talks on Monday and Tuesday in Moscow.

WSJ: Rival Powers Hit Wall on Syria Plan