Russia has warned against any unilateral action on Syria a day after US President Barack Obama threatened "enormous consequences" in the event the government in Damascus uses chemical or biological arms or moves them in a menacing way.
Sergei Lavrov, Russian foreign minister, speaking on Tuesday after meeting China's ambassador, said Moscow and Beijing were committed to "the need to strictly adhere to the norms of international law ... and not to allow their violation".
Qadri Jamil, Syrian deputy prime minister, also speaking in Moscow, dismissed Obama's threat as media fodder.
"Direct military intervention in Syria is impossible because whoever thinks about it ... is heading towards a confrontation wider than Syria's borders," he said at a news conference.
Jamil said the West was seeking an excuse to intervene, likening the focus on Syria's chemical weapons with the run-up to the 2003 invasion of Iraq by US-led forces on what proved to be false claims that Saddam Hussein was concealing weapons of mass destruction.
Jamil also said that President Bashar al-Assad's resignation could be a topic of discussion, though he rejected the idea of making it a precondition for future talks.
"As far as his resignation goes, making the resignation itself a condition for holding dialogue means that you will never be able to reach this dialogue," he said.
"[But] any problems can be discussed during negotiations. We are even ready to discuss this issue."
Victoria Nuland, US state department spokeswoman, responded to Jamil with scepticism, saying "we didn't see anything terribly new there".
Russia and China have opposed military intervention in Syria throughout the 17-month-old revolt against Assad. They have vetoed three UN Security Council resolutions backed by Western and Arab states that would have put more pressure on Damascus to end violence that has cost 18,000 lives.
In-depth coverage of escalating violence across Syria
Although removing Assad is the rebels' top goal, it is unclear at this point in the fighting whether they would be satisfied with his resignation alone. Many probably want Assad to face prosecution, while others have said they want him killed.
The US and its allies have shown little appetite for intervention to halt the bloodshed, unlike last year's comparatively rapid NATO campaign to help topple Libya's Muammar Gaddafi.
But on Monday, Obama used some of his strongest language yet to warn Assad against using unconventional weapons.
"We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is [if] we start seeing a whole bunch of chemical weapons moving around or being utilised," he said. "That would change my calculus."
Chemical arms issue
Syria last month acknowledged for the first time that it had chemical or biological weapons and said it could use them if foreign countries attacked it. Reports in US news media citing national security officials claimed that Washington had observed the movement of certain chemical weapons.
"We cannot have a situation where chemical or biological weapons are falling into the hands of the wrong people," Obama said.
The US-based Global Security website says there are four suspected chemical weapons sites in Syria producing the nerve agents VX, sarin and tabun. It does not cite its sources.
Israel, still formally at war with Syria, has also debated whether to attack the unconventional arms sites, which it views as the biggest threat from the conflict next door.
In the shadow of the deeply unpopular war in Iraq, Obama has been reluctant to embroil the US in Syria and refuses to arm rebels. Some US analysts fear that some of those involved are Islamist fighters equally hostile to the West.
Rebels have seized swathes of territory in northern Syria near Turkey, which now hosts 70,000 Syrian refugees and which has suggested that the UN might need to create a "safe zone" in Syria if that total topped 10,000.
But setting up a safe haven would require imposing a no-fly zone, an idea which Leon Panetta, US defence secretary, said last week was not a "front-burner" issue for his country.
With diplomatic efforts to end the war blocked by divisions between world powers and regional rivalries, Syria faces the prospect of a prolonged conflict that increasingly sets a mainly Sunni Muslim opposition against Assad's Alawite minority.