He said the Syrian government was clearly responsible for the use of chemical weapons that killed more than 1,000 people last month.

He said the US would work with Russia on its proposal to persuade Syria to destroy its chemical weapons stockpile.

But he said the US would maintain the threat of force should diplomacy fail.

Speaking from the White House, President Obama said he had long resisted calls for military action in Syria because he did not believe that force could solve the civil war.

But he said he changed his mind after the alleged chemical weapons attack in the Damascus suburbs on 21 August.

He said he welcomed Russia's proposal as an alternative to military action, but added: "It's too early to tell whether this offer will succeed.

"Any agreement must verify that the Assad regime keeps its commitments. But this initiative has the potential to remove the threat of chemical weapons without the use of force."

President Obama said he had asked the leaders of Congress to postpone a vote to authorise the use of force "while we pursue this diplomatic path".

He confirmed that US Secretary of State John Kerry would meet his Russian counterpart Sergei Lavrov in Geneva on Thursday, adding: "I will continue my own discussions with President (Vladimir) Putin."

The BBC's North America Editor Mark Mardell said the president's address was clear but almost entirely lacking in passion and devoid of new arguments.

Mr Obama's address came after a day of diplomatic wrangling at the UN over the Russian plan for Syria's chemical weapons to be put under international control.

The UK, US and France want a timetable and the consequences of failure spelt out, and Washington has warned it will "not fall for stalling tactics".

Russia said any draft putting the blame on the Syrian government was unacceptable and urged a declaration backing its initiative.