The US and its allies are pressing for military action against President Bashar al-Assad's regime, despite stern warnings against intervention from key Damascus supporters Russia and Iran. And Britain has pushed for a resolution to pave the way for military strikes.
British Prime Minister David Cameron said London is presenting a resolution "condemning the chemical weapons attack by Assad" to a meeting of the UN Security Council's five permanent members, which got under way in New York on Wednesday morning.
"We've always said we want the UN Security Council to live up to its responsibilities on Syria. Today they have an opportunity to do that," he said on Twitter.
UN Secretary General Ban Ki-moon urged the council to "find the unity to act, to use its authority for peace".
Russia, which has already used its veto to block resolutions condemning Syria, said it was premature for the council to act before a UN team inspecting the sites of the alleged attacks releases its findings.
The UN-Arab League envoy to Syria, Lakhdar Brahimi, confirmed that chemical "substances" were used in the attacks that are said to have killed hundreds of people on the outskirts of Damascus on August 21.
Inspectors returned to Damascus on Wednesday afternoon after visiting the eastern Ghouta region of Damascus, the site of one of the reported attacks, and Ban said they would need until at least Friday to complete their work.
The UN chief added that their findings would then be analysed and the result sent to the Security Council for "any action they would deem to take".
Russian news agency RT reported earlier on Wednesday : "Damascus has handed over proof to UN inspectors that Assad’s regime did not deploy chemical weapons, Syrian Deputy Foreign Minister Faisal al-Miqdad told reporters Wednesday."
"Syrian government forces have never used chemical weapons – such claims are just a pretext. We have proof of this, which we passed to the inspectors of the UN commission," Miqdad said.
Brahimi said any military action "must be taken after a decision by the Security Council".
Preparing for war
But there is a precedent for action without a UN resolution, as was the case when Nato forces helped rebels oust Libyan leader Muammar Gaddafi in 2011 .
A senior US official said the country has ruled out unilateral action and is conferring with allies on potential punitive strikes that could last for more than a day.
Any campaign is expected to be limited in scope, likely to last only several days and to target military sites, but not chemical weapons stocks themselves, other sources in the US said.
Analysts expect to see cruise missiles launched from US and allied submarines, ships and possibly warplanes from outside Syria's territorial waters and airspace.
President Barack Obama's deputies are consulting Turkey, Jordan and other partners on contingency plans in preparation for any retaliation by Syria in the event of US-led action, the official said.
Support for military intervention
Israel, along with the US and its allies, blames Assad's regime for the chemical weapons attacks.
"In light of the recent occurrences in the region, the Israel Defence Forces is taking the necessary defensive measures to safeguard the state of Israel," military sources said on Wednesday.
"These measures include both active and passive defence mechanisms".
Army radio reported that the military was moving Iron Dome missile defence systems in the north, as well as one Patriot missile defence battery to western Galilee.
Israeli media said Prime Minister Benjamin Netanyahu convened his eight-member security cabinet for consultations on the Syria situation.
On Tuesday, Netanyahu vowed a fierce reaction to "any attempt to hurt us" from Syria or its allies, in a possible reaction to a US attack.
But army spokesperson Brigadier General Yoav Mordechai downplayed tensions on Wednesday, saying there was no room for alarm at this stage.
The Organisation of Islamic Cooperation (OIC) has condemned alleged poison gas attacks in Syria, blaming the government and calling for "decisive action" in response.
The world's largest grouping of Muslim nations "stressed the need to hold the Syrian government legally and morally accountable for this heinous crime and to bring its perpetrators to justice".
The OIC called on the UN Security Council “to discharge its duty of preserving international security and stability, taking a unified position against this monstrous crime and its perpetrators.
"This attack is a blatant affront to all religious and moral values and a deliberate disregard of international laws and norms, which requires a decisive action," it said.
OIC chief Ekmeleddin Ihsanoglu said he "remains convinced of the need to urgently work out a political solution to extricate Syria from this bloody crisis and to restore peace and security in the country".
Opposition to military intervention
Countries such as Poland and Belgium oppose military intervention in Syria.
Poland voiced reservations about military action in Syria on Wednesday in a rare departure from toeing the same line as the US.
"I'm not convinced that an armed attack will stop the crimes," Prime Minister Donald Tusk told reporters. "I understand the reasoning, but I don't share the belief and enthusiasm of those who think that such an operation could bring about positive effects."
Tusk's announcement that Poland does not plan to take part in a military intervention came as the US and its allies press their case for such action against Assad's regime, despite stern warnings from Syrian allies Russia and Iran.
Belgium, which joined military action in Libya and Mali, is "not yet convinced" of the merits of intervening in Syria and wants proof that Damascus used chemical weapons against its people.
"I am not yet convinced. What we want is to receive information showing the use of these arms," Foreign Minister Didier Reynders said on Wednesday in an interview aired by state broadcaster RTBF.
Belgium hopes to get such information from the United Nations, "but should France, the US and Britain have information on this subject, they could share it with their Nato allies", Reynders said.
Protecting civilians
Human Rights Watch (HRW) says civilians must be protected at all costs. But "if there is a military intervention, all warring parties must strictly adhere to the laws of war", which forbid deliberate attacks against civilians and the use of weapons such as cluster munitions or antipersonnel landmines.
"Military action carried out in the name of upholding a basic humanitarian norm – you don't gas children in their sleep – will be judged by its effect in protecting all Syrian civilians from further unlawful attacks, whether chemical or conventional," said HRW executive director Kenneth Roth. – AFP, Reuters