WASHINGTON/LONDON: Syria said on Tuesday it would sign an international chemical weapons treaty and admit the scale of its chemical weapons stockpile for the first time.

The foreign minister, Walid al-Moallem, said his country would halt production of chemical arms, disclose the location of its existing arsenal and allow access to UN inspectors in accordance with the Chemical Weapons Convention.

Joining the convention implied a commitment to destroy the poison gases and nerve agents thought to be in Syria’s possession but a battle was looming at the UN over whether the timetable for Syrian disarmament should be enforced by the threat of military action.

The US, Britain and France are preparing a hard-edged security council resolution backed by the possible use of force. Russia is proposing a much milder non-binding council declaration. As both sides manoeuvred for tactical advantage, Russia first summoned an emergency council meeting yesterday then abruptly cancelled it.

Vladimir Putin, the Russian president, insisted the disarmament process would work “only if the US and those who support it on this issue pledge to renounce the use of force, because it is difficult to make any country — Syria or any other country in the world — unilaterally disarm if there is military action against it under consideration”. Russia proposes to work with the Assad regime and the UN secretariat to lay out a “workable, precise and concrete” disarmament plan with a timetable but no enforcement mechanism.

After a phone conversation with his Russian counterpart, the French foreign minister, Laurent Fabius, admitted: “As I understood, the Russians at this stage were not necessarily enthusiastic — and I’m using a euphemism, to put all that into the framework of a UN binding resolution.”

The US, UK and France all stressed that they would not allow Russia or Damascus to play for time. The US secretary of state, John Kerry, told a hearing of the House of Representatives armed services committee that the US was waiting for details of the Russian proposal, “but we’re not waiting for long”.

He said: “President Obama will take a hard look at it. But it has to be swift, it has to be real, it has to be verifiable. We have to show Syria, Russia and the world we are not going to fall for stalling tactics.”

David Cameron delivered the same message in London, saying the UK did not want the Russian disarmament proposal to be “some delaying tactic, some ruse to buy time for a regime that must act on chemical weapons”.

Referring to the planned UN resolution, the British prime minister said “there would have to be consequences” if it wasn’t done.

However, the western powers’ tough rhetoric is weakened by the lack of enthusiasm at home for military action. Parliament has ruled out British involvement in punitive strikes, and Barack Obama faces stiff resistance in Congress.

“I think there is a high risk of another car crash at the security council,” said Richard Gowan of the centre for international co-operation at New York University. “It will be very, very difficult for Obama to accept a resolution that doesn’t involve a threat to Assad. Putin is daring him to walk away from the UN and go back to Washington, knowing he can’t count on support there. The Russians hope that when he’s faced with that trap he will climb down.”

The White House abandoned its earlier plan to seek open-ended authorisation for punitive air strikes in response to the Assad regime’s alleged use of chemical weapons in a civilian massacre in eastern Damascus on 21 August.

Instead, the Obama administration was working with a bipartisan group of eight senators to craft a new resolution that would set a deadline for Syrian co-operation with the UN on disarmament, and authorise the use of force if that deadline was broken.

The Senate suspended plans to vote on military authorisation after meeting with Obama to discuss the proposed Russian deal. The majority leader, Harry Reid, said “it’s important we do this well, not quickly” but called on Syria to show that its offer to hand over chemical weapons to international observers was “not a ploy”.

A fellow Democrat, Joe Manchin, who has opposed military action, said he was heartened by the meeting and said he would pursue a separate resolution giving the Syrians time to comply.

On Tuesday Human Rights Watch said evidence from the massacre of civilians in eastern Damascus last month strongly suggested the Syrian government carried out the chemical weapons attacks.

The report based its conclusions on testimony from witnesses and medical staff as well analysis of the armaments used, which HRW said were of a type used only by the Syrian military. The effect on the victims pointed to a nerve agent, “most likely sarin”.

It said it was impossible so far to give an exact death toll, but noted that the estimate in just one district was over 700 and that Medecins Sans Frontieres had reported that at least 3,600 people were treated for symptoms consistent with exposure to neurotoxins.

By arrangement with the Guardian