US President Barack Obama has vowed that Syria will be held to account if it fails to live up to its promises to surrender chemical weapons.

It comes as he faced questions about how a deal brokered by US and Russian diplomats would be enforced.

In a statement, Mr Obama said a framework deal was an important, concrete step toward getting Syria's chemical weapons under international control so they can ultimately be destroyed.

The deal emerged from Geneva talks between US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov.

"While we have made important progress, much more work remains to be done," President Obama said.

US president criticised over "muddled message"

He has been bombarded with criticism for his handling of Syria and a muddled message.

First, he took US forces to the brink of a military strike over a 21 August poison gas attack in Syria that Washington blames on Syrian President Bashar al-Assad.

He then asked Congress to authorise the strike, but less than a week later requested lawmakers hold off on a vote to allow diplomacy more time.

He now faces questions about how the Syrian diplomatic deal will be enforced.

Senior administration officials said yesterday that the US will not insist that the use of military force be included among the consequences Syria would face in a UN Security Council resolution being negotiated, in order to avoid a Russian veto.

Mr Obama, in his statement, insisted that the US "remains prepared to act" should diplomatic efforts fail.

But Republican Senators John McCain and Lindsey Graham, who have sharply criticised President Obama's handling of Syria, said the deal is meaningless unless backed up with the threat of military force.

US and Russia agree chemical weapons plan for Syria

US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov have agreed that the United Nations must be allowed to inspect all sites of chemical weapons in Syria.

The agreement came after nearly three days of talks between US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov.

Mr Kerry said that, under the pact, Syria must submit a "comprehensive listing" of its chemical weapons stockpiles within one week.

Mr Kerry, at a press conference with Mr Lavrov, said that under the agreement UN weapons inspectors must be on the ground in Syria no later than November.

The goal, he said, is the complete destruction of Syria's chemical weapons by the middle of 2014.

Mr Kerry and Mr Lavrov said that if Syria does not comply with the agreement, which must be finalised by the Organisation for the Prevention of Chemical Weapons, it would face consequences under Chapter 7 of the UN Charter.

Chapter 7 of the UN Charter contains sanctions and military action.

Mr Kerry said there was no agreement on what those measures would be.

US President Barack Obama, Mr Kerry said, reserves the right to use military force in Syria saying: "There's no diminution of options."

Mr Lavrov said of the agreement, "There (is) nothing said about the use of force and not about any automatic sanctions.

The Geneva talks were part of a diplomatic push that prompted President Obama to put on hold his plans for US air strikes on Syria.

Moscow's proposal to hold talks spared Mr Obama from facing a vote in Congress on military action that he had appeared increasingly likely to lose at this stage.

Meanwhile, a new Reuters/Ipsos poll indicates that 62% of Americans oppose US military intervention in Syria.

Assad promised deal to avoid US air strikes

Last Thursday, the United Nations said it had received a document from Syria on joining the global anti-chemical weapons treaty.

The move by Syrian President Bashar al-Assad was promised as part of a deal to avoid US air strikes.

Mr Assad told Russian state television that he would finalise plans to abandon his chemical arsenal only when the US stopped threatening to attack.

Elsewhere, the Syrian opposition coalition is holding a meeting  in Istanbul to appoint a provisional prime minister in order to have more credibility.

The head of the opposition Syrian Supreme Military Council General Selim Idris said the US-Russian agreement was a blow to the two-and-a-half-year uprising to remove President Assad from power.

General Selim Idris said the deal would allow President Assad to escape being held accountable for killing hundreds of civilians in a poison gas attack on Damascus on 21 August.