WASHINGTON (REUTERS) - US President Barack Obama will pledge to explore a Russian diplomatic initiative for Syria in a speech to be delivered on Tuesday night (Wednesday 9:00 am, Singapore time), an administration official said.

Mr Obama will express skepticism about the Russian proposal to put Syria's chemical weapons under international control but will seek to see if it is for real, the official said.

The stakes are high for Mr Obama, who also will try to persuade war-weary Americans that any US military action contemplated by his administration against Syria would be limited in scope and duration.

Mr Obama will explain to Americans why it is in US national security interests for Syria to face consequences for an Aug. 21 chemical weapons attack that US officials say killed 1,429 people.

Mr Obama and his national security advisers say to do nothing in response to the poison gas onslaught would risk emboldening US enemies to try to gain access to chemical weapons and use them against American targets.