Obama, speaking in a TV interview taped before Saturday's announcement of the chemical weapons deal, said Russian President Vladimir Putin is "protecting" Assad and doesn't share American "values" in Syria.
"He has a different attitude about the Assad regime," Obama told ABC's "This Week."
"But what I've also said to him directly is that we both have an interest in preventing chaos, we both have an interest in preventing terrorism. The situation in Syria right now is untenable. As long as Mr. Assad's in power, there is going be some sort of conflict there."
The U.S.-Russian agreement has won broad backing around the world, including from China, which is a permanent member of the U.N. Security Council. France also welcomed the deal, but French Foreign Minister Laurent Fabius cautioned during a visit Sunday in Beijing that it was only the "first stage."
In Cairo, the Arab League also approved of the U.S.-Russian deal. Secretary-General Nabil Elaraby said the agreement helps move toward a political settlement to the crisis.
"All parties are capable and influential enough to do their part in the U.N. Security Council to ensure a comprehensive cease-fire in Syria ... and to move toward negotiations in Geneva to achieve a peaceful settlement to the Syrian crisis," Elaraby said in a statement.
Germany offered Sunday to help destroy Syrian chemical weapons. Foreign Minister Guido Westerwelle said in a statement that Berlin is "prepared to make a technical or financial contribution to the destruction of chemical weapons from Syria." He didn't elaborate, but officials say Germany has helped destroy chemical weapons in Libya and elsewhere in the past.
The Syrian opposition warned that the Assad regime may just be playing for time and said the threat of force must remain on the table. It added that securing Syria's chemical weapons "must be for achieving justice and bringing the perpetrators of chemical weapons to the international court."
The Syrian National Coalition also repeated its calls for military aid, to "force the regime to end its military campaign and accept a political solution that leads to the democratic transformation of Syria."
The U.S. and its allies have balked at sending heavy weapons to the rebels, fearful the arms could land in the hands of extremists who are among the most effective fighters in the opposition ranks. Washington announced plans months ago to deliver some weapons to the opposition, but rebels say they have yet to receive anything.
Associated Press writers Matthew Lee and Josef Federaman in Jerusalem, Aya Batrawy in Cairo, Lynn Berry in Moscow and Louise Watt in Beijing contributed to this report.
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