He rejected suggestions that the summit fell short of expectations by failing to call for new tough sanctions on Iran for its crackdown on democracy advocates after its disputed presidential election.
"What we wanted is exactly what we got - a statement of unity and strong condemnation," Obama told a news conference. He said the leaders' declaration was even more significant because it included Russia, "which doesn't make statements like that lightly."
He said world leaders will reevaluate their posture toward Iran at a meeting in Pittsburgh in September of the world's 20 major industrial and developing economies.
Obama told reporters that leaders "remain seriously concerned about the appalling events of Iran's presidential election." He said the world would "take stock of Iran's progress" and watch its behavior.
Leaders have made clear that for Iran to take its "rightful place" in the world, the country must adhere to international standards and behave responsibility, Obama said.
On a pressing issue back home, Obama acknowledged that his top legislative priority - health care overhaul - had encountered rocky going in Congress during his overseas trip, with opposition building among both Republicans and economically conservative Democrats.
But he said he still hopes to get the measure passed before Congress begins its August recess.
"I'm confident we're going to get it done," he said. Asked if his timetable was "do or die," Obama responded: "I never believe anything is do or die. But I want to get it done by the August recess."
Obama, six months in office, said he supports a streamlining of summits - the G-8, G-20 and NATO - and attending fewer of those meetings. He said the United Nations is in need of reform, but international summits fill a gap left by a U.N. structure that doesn't leverage its power as effectively as it could.