New York's main contract, West Texas Intermediate for delivery in October, eased 55 cents to $106.84 a barrel, while Brent North Sea crude for October was down seven cents at $111.18.

In a live address to the nation from the White House late Tuesday, Obama said delaying a decision on military intervention was necessary to give Russia's plan to neutralise its ally's chemical weapons a chance.

"I have therefore asked the leaders of Congress to postpone a vote to authorise the use of force while we pursue this diplomatic path," Obama said, noting that Secretary of State John Kerry would head to Geneva to meet his Russian counterpart on Thursday.

However he warned that it was too early to tell if Russia's plan would work, and said cruise missile destroyers would remain stationed in the Mediterranean, ready to strike on the Assad regime.

WTI had closed $2.13 lower in New York ahead of the national address as Syria promised to give up its chemical weapons, while Brent was $2.47 off.

"President Obama now seems to be walking away from his earlier hard stance on Syria, and this means that we are likely to see the recent risk premium on crude dissolve," Desmond Chua, market analyst at CMC Markets in Singapore, told AFP.

Syria's promise "eased concerns that the conflict will escalate and disrupt oil shipments from the Middle East", Malaysian banking group CIMB said in a note.

Analysts said investors will also be watching the latest US crude stockpiles data to be released Wednesday for clues about demand in the world's top oil consumer. (AFP)