GENEVA: Russia and the United States put aside bitter differences over Syria to strike a deal on Saturday that by removing President Bashar al-Assad's chemical arsenal may avert US military action against him.

After three days of talks in Geneva, US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov demanded Assad account for his secret stockpile within a week and let international inspectors eliminate all the weapons by the middle of next year - an “ambitious” target, Kerry said.

The accord leaves major questions unanswered, including how feasible such a major disarmament can be in the midst of civil war and at what point Washington might yet make good on a continued threat to attack if it thinks Assad is reneging.

Under the Geneva pact, the United States and Russia will back a UN enforcement mechanism. But its terms are not yet set. Russia is unlikely to support the military option that President Barack Obama said he was still ready to use.

“If diplomacy fails, the United States remains prepared to act,” Obama said. “The international community expects the Assad regime to live up to its public commitments.”

To that end, the Pentagon said US military forces were still positioned to strike, if ordered.

But for Assad's opponents, who two weeks ago thought US missile strikes were imminent in response to a gas attack on rebel territory, the deal was a blow to hopes of swinging the war their way. Kerry and Lavrov said it could herald broader peace talks, as warplanes hit rebel positions again near Damascus.

The accord, however, was as much about US-Russian ties as it was about Syria. The conflict has chilled relations to levels recalling the Cold War.

In reaching a bilateral deal after what one US official described as three days of “hard-fought” debate, Moscow and Washington can each count benefits.

For Russian President Vladimir Putin, it brings management of the Syrian crisis back to the United Nations. For Obama, it solves the dilemma created by Congress's reluctance to back military strikes that he was preparing without a UN mandate.

Lavrov told a joint news conference in Geneva, “It shows that when there is a will ... Russia and the United States can get results on the most important problems.

“The successful realisation of this agreement will have meaning not only from the point of view of the common goal of eliminating all arsenals of chemical weapons, but also to avoid the military scenario that would be catastrophic for this region and international relations on the whole.”

China, which has opposed military intervention in Syria all along, welcomed the deal.

“We believe that this framework agreement has ameliorated the present explosive and tense situation in Syria,” Foreign Minister Wang Yi told visiting French Foreign Minister Laurent Fabius.

Kerry acknowledged that further success was far from guaranteed: “The implementation of this framework, which will require the vigilance and the investment of the international community, and full accountability of the Assad regime, presents a hard road ahead,” he said.

Despite a measure of camaraderie on display in banter between the two men during the presentation of the two-page framework agreement, they remained openly at odds over the US willingness to use force in Syria without UN backing.

Deal offers way out

Having taken the surprise decision two weeks ago to seek congressional approval for strikes to punish Assad for using poison gas, Obama faced a dilemma when lawmakers appeared likely to deny him authorization.

They cited unease about inadvertently helping Islamist militants among the rebels and a wariness of new entanglements in the Middle East after wars in Iraq and Afghanistan.

The weapons deal proposed by Putin, intent on restoring some of the influence Moscow lost with the Soviet collapse two decades ago, offered Obama a way out.

But Obama has been bombarded with criticism for his handling of Syria and a muddled message, moving the United States toward, and then back from the brink of striking Syria over an August 21 poison gas attack that Washington blames on Assad.

Republican Senators John McCain and Lindsey Graham, who advocate deeper US involvement in Syria's civil war, blasted the deal, saying it would effectively allow Assad months to "delay and deceive."

"It requires a willful suspension of disbelief to see this agreement as anything other than the start of a diplomatic blind alley, and the Obama administration is being led into it by Bashar Assad and Vladimir Putin," they said.

Carl Levin, a Democrat aligned with Obama and head of the Senate Armed Services Committee, hailed the agreement and noted it did not restrict the United States from supporting the moderate Syrian opposition or acting unilaterally, if needed.

Under the terms of the US-Russian agreement, the UN Security Council - on which Russia has a veto - will oversee the process. Syria must let the OPCW complete an initial inspection of its chemical weapons sites by November.

Kerry said Assad must produce a "comprehensive listing" of its chemical weapons within a week. The goal is to complete destruction of Syria's arsenal in the first half of 2014.

The agreement states that a Security Council resolution should allow for regular assessments of Syria's behavior and "in the event of non-compliance ... the UN Security Council should impose measures under Chapter VII of the UN Charter".

Chapter VII can include force but can be limited to other kinds of sanction. When Kerry said the council "must" impose measures under Chapter VII, Lavrov interrupted to point out that the agreed text says only it "should" impose penalties.

"There's no diminution of options," Kerry said, noting Obama's right under US law to order military action, with or without support from Congress or any international body.

The Pentagon said it had made no change to the forces it had lined up. A spokesman said, "The credible threat of military force has been key to driving diplomatic progress."

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

Putin has supported Assad's contention that the sarin gas attack on August 21, which Washington says killed over 1,400 civilians, was the work of rebels trying to provoke Western intervention.

Lavrov said, however, that Russia would support UN punishment for anyone whose guilt was clearly proven.

A new round of argument about responsibility for the August 21 deaths is likely in coming days, once UN inspectors deliver their report on the incident to the world body.