Russia and the United States may have "different interpretations" of the accord on dismantling Syria's chemical weapons, a prominent Russian lawmaker warned Sunday.

"The main question now is to see whether the Syrian settlement becomes the subject of different, even opposite, interpretations in the United States and Russia," said Alexei Pushkov, chairman of the lower house Duma's foreign affairs committee.

Syria's opposition demanded on Sunday that the international community impose a ban on the Damascus regime's use of its air power in urban areas, in addition to its chemical weapons.

"The Syrian National Coalition insists that the prohibition of chemical weapons, the use of which has left more than 1,400 civilians dead, be extended to the use of ballistic missiles and aircraft against urban areas," it said in a statement.

China's foreign minister on Sunday welcomed the deal between the United States and Russia to eliminate Syria's chemical weapons, which headed off the prospect of U.S. strikes against Bashar Assad's regime.

"The Chinese side welcomes the framework agreement between the U.S. and Russia. This agreement will enable tensions in Syria to be eased," Wang Yi said at a meeting with his visiting French counterpart Laurent Fabius.

The United Nations on Saturday formally accepted Syria's application to join the chemical weapons convention, a spokeswoman said.

The move adds another piece to the diplomatic plan to end the threat of a U.S. military strike on President Bashar Assad over the suspected use of chemical arms in the 30-month-old Syria conflict.

Iran's deputy foreign minister said Saturday the United States no longer has a pretext to attack Syria, following a deal struck to eliminate that country's chemical weapons.

"The new situation means in fact that any pretext for the United States and certain countries to engage in military action against Syria has been removed," Hossein Amir-Abdollahian said.

The countdown has begun on a dangerous, tough mission to eliminate Syria's chemical weapons, with the regime given just seven days to lift the veil on its secret stockpile and allow inspectors into the war-torn country.

In whirlwind, round-the-clock diplomacy in Geneva, the United States and Russia hammered out a landmark framework for dismantling and destroying one of the world's largest stockpiles of chemical arms.

A pro-Kremlin lawmaker and former Olympic gold medalist faced a racism row Saturday after she posted a photo-collage of President Barack Obama juxtaposed with a banana on Twitter.

Irina Rodnina posted on Twitter a photomontage that purports to show Obama and his wife gazing at a hand in the foreground holding up a banana.

Making Russia agree to take U.N.-backed action against Syria if President Bashar Assad breaches a chemical weapons deal announced Saturday is a victory for the United States, diplomats said.

"Russia has been so hostile to U.N. action on the Syria war that this is a breakthrough by itself," said one U.N. diplomat.

U.N. leader Ban Ki-moon on Saturday welcomed a Russian-U.S. deal on Syria's chemical weapons but said it must be a stepping stone to ending the "appalling suffering" of Syrians, a spokeswoman said.

Ban pledges U.N. support to implementing the accord reached by Russia's Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry, said a U.N. spokeswoman Vannina Maestracci.

Syria's rebel Free Syrian Army chief rejected Saturday a U.S.-Russian deal to eliminate Syria's chemical weapons by mid-2014.

"We cannot accept any part of this initiative," General Selim Idriss told reporters in Istanbul.