MOSCOW (Reuters) - Russian President Vladimir Putin and U.S. President Barack Obama discussed the idea of placing Syria's chemical weapons arsenal under international control on the sidelines of a G20 summit last week, Putin's spokesman said on Tuesday.

"The issue was discussed," spokesman Dmitry Peskov said by telephone. He would not say who raised the issue or give other details.

Russia announced its proposal to put Syrian chemical weapons under international control on Monday. Hours earlier, U.S. Secretary of State John Kerry had said Syrian President Bashar al-Assad could avoid a U.S. military strike by surrendering all his chemical weapons within a week but added that Assad "isn't about to do it and it can't be done".

(Reporting by Alexei Anishchuk; Writing by Steve Gutterman, Editing by Timothy Heritage)