The United States is setting an unrealistic timeframe for Syria to hand over its chemical weapon arsenal, a senior Russian lawmaker said Saturday as Moscow and Washington entered a third day of talks.

The United States is setting an unrealistic timeframe for Syria to hand over its chemical weapon arsenal, a senior Russian lawmaker said Saturday as Moscow and Washington entered a third day of talks.

"The demand by the United States to hand over chemical weapons to international control in two or three weeks is simply unprofessional," Alexei Pushkov, the head of the Russian parliament's foreign affairs committee, wrote on Twitter.

"In Syria there are at least 42 storage facilities, some of them in battle zones," he said.

US officials said Friday that the White House expected that it would take around two weeks to discover whether the Russian-led initiative to take President Bashar al-Assad's chemical weapons under international control was viable.

The United States and Russia are negotiating over how much time Syria can be given to comply with the terms of the international convention banning chemical weapons and declare its full stockpile.