U.S. President Barack Obama says a proposal to put Syria's chemical weapons under international control to avoid U.S. military strikes could be a potential breakthrough.

Obama told NBC News in an interview Monday that he remains skeptical that Syria will follow through and turn over its stockpile, so he's taking a statement from Damascus "with a grain of salt initially." But Obama said he would prefer to have a diplomatic solution to the crisis rather than launch a military attack, and called it "a potentially positive development."

Obama made the comments as he gave a series of six television network interviews on the crisis in Syria.

He also acknowledged he may not be able to secure congressional support for a military strike on Syria.

"I wouldn't say I'm confident" of getting it, Obama told NBC.

"It's fair to say that I haven't decided" on a next move, Obama said, if Congress rejects military action.

Obama will address the U.S. people in a speech from the White House on Tuesday at 9 p.m. ET

Earlier in the day, Syria said it welcomes a Russian proposal to place its chemical weapons under international control and then destroy them, in the Mideast country's first tacit acknowledgment that it possesses such munitions, but neither Damascus nor Moscow offered a time frame or any other specifics for the plan.

A Free Syrian Army fighter moves along a trench with his weapon to avoid forces loyal to Syria's President Bashar al-Assad in eastern al-Ghouta, near Damascus on Sept. 8. (Msallam Abd Albaset/Reuters)

The statement by Syrian Foreign Minister Walid al-Moallem appeared to mean that diplomatic efforts to end Syria's 2½-year civil war were gaining momentum. But it remained to be seen whether it represented a genuine goodwill gesture by Syria or simply an attempt by Syrian President Bashar al-Assad to buy more time before a possible French or U.S. military attack.

"Syria welcomes the Russian proposal out of concern for the lives of the Syrian people, the security of our country and because it believes in the wisdom of the Russian leadership that seeks to avert American aggression against our people," al-Moallem said during a visit to Moscow, where he held talks with his Russian counterpart, Sergey Lavrov.

Moallem, who spoke to reporters through an interpreter after Russia expressed hope the proposal could avert military strikes against Syria, stopped short of saying explicitly that Assad's government accepted it.

He would not give any further details in his brief statement and didn't take any questions from reporters.

Russia said earlier Monday it is willing to push Syria to place its chemical weapons under international control and then dismantle them, in Moscow's strongest concession yet in the three weeks since the Assad regime allegedly deployed a lethal nerve agent against its own citizens.

Russia's proposal confirmed for the first time from Syria's most important international ally that the Syrian government possesses chemical weapons, and Moallem's welcome was a tacit acknowledgment.

Russia's foreign minister said that if Russia's proposal would help avert a possible U.S. strike on Syria, Russia will start work "immediately" to persuade Syria to relinquish control over its chemical arsenals.

The U.S. State Department said it would take a "hard look" at the Russian idea, but would treat it with "serious skepticism" because it might be a stalling tactic and because Syria has consistently refused to destroy its chemical weapons in the past.

In New York, United Nations Secretary General Ban Ki-moon advocated similar measures to Russia's plan, saying he may ask the Security Council to demand Syria move its chemical arms stocks to sites where they can be safely stored and destroyed.

Ban said he may also ask the 15-country body to demand that Syria join the international anti-chemical weapons convention, a treaty that Damascus has never signed.

"Two and half years of conflict in Syria have produced only embarrassing paralysis in the Security Council," Ban said.

'Expect every action,' Assad warns U.S.

The disarmament proposal came as Assad warned of possible reprisals if the United States attacks Syria, saying that if there were military strikes, Americans can "expect every action."

Assad's comments were in a television interview with CBS conducted in Damascus in which he also denied involvement in the Aug. 21 assault that is widely believed to have used chemical weapons. Assad said the evidence was not conclusive that there had been a chemical attack.

He said that if there were U.S. attacks on Syria, the United States "should expect everything" in response.

Assad added in the same interview that any strike against his regime will provide "direct support" to an "al-Qaeda offshoot," an apparent reference to militants, linked to the extremist group, who have aligned with the Syrian opposition.

Russia and Syria both urged the United States on Monday to focus on efforts to convene a peace conference and not on military action.

Lavrov said a U.S. military strike could lead to the spread of terrorism, and Moallem accused President Barack Obama of backing terrorists, drawing comparisons with the attacks on the United States on Sept. 11, 2001.

China, meanwhile, urged the U.S. to proceed with extreme caution and to respect UN discussions on Syria, after Washington said it was not seeking Security Council approval for possible military action.

The U.S. "should return to the United Nations Security Council framework to seek consensus and appropriately handle the Syria issue," Foreign Minister Wang Yi told U.S. Secretary of State John Kerry in a telephone call late on Sunday night.

China has repeatedly called for an impartial investigation by UN chemical weapons inspectors into the attack in Syria. It has also said that whoever used chemical weapons had to be held accountable.

'Turn it over, all of it'

The Russian disarmament proposal followed a statement by Kerry earlier Monday that Syria could avoid a military strike by turning over its chemical weapons stockpile. Asked by a reporter whether there was anything Assad's government could do to stop any attack, Kerry said: "Sure, he could turn over every single bit of his chemical weapons to the international community in the next week — turn it over, all of it without delay and allow the full and total accounting [of it]. But he isn't about to do it and it can't be done."

A spokeswoman for the U.S. State Department later said Kerry was speaking rhetorically — making a point about the "impossibility" of co-operation by Assad — though by mid-day the idea appeared to have gained momentum.

Kerry added that he was confident of the evidence that the United States and its allies have presented to support their case that Assad's forces used chemical weapons. But he said he understood concerns, given that the 2003 Iraq invasion was launched following faulty intelligence that Iraq had weapons of mass destruction.

A UN panel probing possible war crimes and other human rights abuses in Syria, including the use of chemical weapons, is expected to publish a report on Wednesday. That would likely lead to a resolution at the UN's Human Rights Council.

A separate report from UN weapons inspectors is also expected later this week, while the U.S. Congress debates whether to allow limited strikes on Syria.

Regime tries to retake village

In Syria, regime troops launched an attack Monday on hills overlooking a Christian-majority village near the capital, two days after rebel forces captured the ancient community, an activist group said.

The Britain-based Syrian Observatory for Human Rights said fighters from the al-Qaeda-affiliated Jabhat al-Nusra or Nusra Front and the Qalamon Liberation Front still control Maaloula, an ancient village that is home to two of the oldest surviving monasteries in Syria. Rebels captured the village on Saturday.

The battle has thrown a spotlight on the deep-seated fears that many of Syria's religious minorities harbour about the growing role of Islamic extremists on the rebel side in Syria's civil war.