BEIRUT (AP) — Syria’s main opposition bloc on Tuesday urged the West to strike Syrian President Bashar Assad’s regime despite Russia’s initiative to have Damascus surrender its chemical weapons to international control, dismissing the proposal as maneuver to escape punishment.

Even as the Syrian National Coalition tried to push back against the proposal, momentum for it was building. In Moscow, Syrian Foreign Minister Walid al-Moallem said Tuesday that Damascus accepts the initiative, saying it did so to "uproot U.S. aggression."

U.S. Secretary of State John Kerry said Monday that Assad could resolve the crisis by surrendering control of "every single bit" of his arsenal to the international community by the end of the week.

The proposal is a sudden shift after the United States was preparing for weeks for possible strikes against Assad’s regime, which Washington accuses of carrying out an alleged chemical attack near Damascus on Aug. 21 that killed hundreds. Damascus denies its forces were behind the attack. A leading international human rights group said Tuesday that evidence strongly suggests Assad’s forces fired rockets with warheads containing a nerve agent — most likely sarin.

The SNC, which is the main political opposition umbrella group, has been cheering for international military action, hoping a blow would shift the bloody war of attrition between rebels and Assad’s forces, with more than 100,000 dead in more than 2 1/2 years of fighting.

In a statement Tuesday, the coalition said Moscow’s proposal "aims to procrastinate and will lead to more death and destruction of the Syrian people."

"A violation of international law should lead to an international retaliation that is proportional in size," the group said. "Crimes against humanity cannot be dropped by giving political concessions or by handing over the weapons used in these crimes."

In Israel, senior politicians also voiced skepticism about Russia’s proposal.

Avigdor Lieberman, a close ally of Prime Minister Benjamin Netanyahu and the head of the parliament’s foreign affairs and defense committee, told Israel Radio that Assad is using the proposal to "buy time." He also said the logistics of a weapons transfer are unclear.

Israeli President Shimon Peres warned on Monday that negotiations over a weapons transfer would be "tough" and that Syria is "not trustworthy."

Washington has cited intelligence reports as saying the August attack on Ghouta, a sprawling, rebel-held suburb of Damascus, killed at least 1,429 people, including more than 400 children, though other estimates are much lower.

The Obama administration has been struggling to build support at home and abroad for limited punitive strikes against Assad’s regime.

President Barack Obama is seeking authorization from Congress for U.S. intervention in Syria, and later Tuesday he was to present his case to the American people in a nationally televised speech from the White House.

In Moscow, Foreign Minister Sergey Lavrov said Tuesday that Russia is working with Syria on the details of its initiative, which would place Damascus’ chemical weapons under international control for subsequent dismantling.

A detailed plan of action will be presented shortly, Lavrov said, adding that Russia will finalize the plan together with U.N. Secretary General Ban Ki-moon and the Organization for the Prohibition of Chemical Weapons.

In a sign that there is little international appetite to join forces against Assad, France said it will propose a U.N. Security Council resolution Tuesday to put Syria’s chemical weapons arsenal under international supervision and to eventually destroy them.

In Syria’s first reaction to Kerry’s comments a front page editorial in Al-Baath newspaper praised the Russian proposal, but said the initiative is unlikely to please the Americans. The paper, a mouthpiece of the ruling Baath Party, slammed Kerry as "arrogant" for giving Syria a week to handover its chemical weapons.

"He is aware that this deadline is impossible for technical and logistic reasons," the editorial said.

Al-Moallem’s remarks on the Russian proposal were the closest Damascus has come to acknowledging that it possesses chemical weapons. But his vague statement accepting the initiative left open questions over the extent of Syria’s cooperation.

Meanwhile, New York-based Human Rights Watch said it examined documents from the alleged chemical attack outside Damascus and concluded that the nerve agent used was "most likely, sarin."

In a 22-page report released Tuesday, the group said it was unable to go to Ghouta to collect remnants of weapons, environmental and bodily samples such as hair and blood of the victims to test for the chemical agent, but that it sought technical advice from an expert on the detection and effects of chemical warfare agents.

The New York-based group also said it analyzed witness accounts and "the type of rockets and launchers used" in the Ghouta attack. HRW experts studied documented medical symptoms of the victims and analyzed activist videos posted on the Internet after the attack, the group said.

"This evidence strongly suggests that Syrian government troops launched rockets carrying chemical warheads into the Damascus suburbs that terrible morning," said Peter Bouckaert, HRW’s emergencies director.

Symptoms of the victims from the attack "provide telltale evidence about the weapon systems used," he added.

Assad and officials from his government have denied allegations their forces used chemical agents and have blamed the Syrian rebels, whom they call terrorists, for staging the attack to gain international sympathy.

In an interview on CBS Monday, Assad warned that there will be retaliation against the U.S. for any military strike against Syria.

"You should expect everything. Not necessarily from the government," he said when asked to elaborate, an apparent reference to the possibility the regime could unleash allied militant groups such as the Iranian-backed Lebanese militant group Hezbollah. He added, addressing the U.S., that it would "pay the price if you are not wise with dealing with terrorists."

Assad also denied that he was behind the attack, saying his soldiers were "in another area" at the time and insisting that no evidence has been presented.