In Copenhagen, President Obama declared Friday a "meaningful and unprecedented breakthrough" had been reached on a climate change deal.
The Associated Press reports the deal was among the U.S., China and three other countries. The President said much work is still needed to reach a legally binding treaty.
"It is going to be very hard, and it's going to take some time," he said near the conclusion of a 193-nation global warming summit. "We have come a long way, but we have much further to go."
The President said there was a "fundamental deadlock in perspectives" between big, industrially developed countries like the United States and poorer, though sometimes large, developing nations. Still he said this week's efforts "will help us begin to meet our responsibilities to leave our children and grandchildren a cleaner planet."
The deal as described by Obama reflects some progress helping poor nations cope with climate change and getting China to disclose its actions to address the warming problem.
But it falls far short of committing any nation to pollution reductions beyond a general acknowledgment that the effort should contain global temperatures along the lines agreed to at a conference of the leading economic nations last July.
Obama suggested Friday's agreement among the five key countries would be adopted by the larger summit in its closing hours.
"I am leaving before the final vote," he said. "We feel confident we are moving in the direction of a final accord."
If the countries had waited to reach a full, binding agreement, "then we wouldn't make any progress," Obama said. In that case, he said, "there might be such frustration and cynicism that rather than taking one step forward we ended up taking two steps back."
The limited agreement by the U.S., China, Brazil, India and South Africa reflected the intense political and economic obstacles that had blocked a binding accord to restrict emissions of "greenhouse gases" believed to be causing a dangerous warming of the Earth.
The accord calls for the participating countries to list specific actions they have taken to control emissions and the commitments they are willing to make to achieve deeper reductions.
There would be a method for verifying reductions of heat-trapping gases, a senior administration official said, speaking on the condition of anonymity before Obama made his comments.