President Donald Trump was evasive yesterday over when the United States might fire missiles at Syria in retaliation for an alleged chemical weapons attack, saying they could come at any time.
Tension was mounting among top world powers over the alleged chemical attack against civilians in the Syrian town of Douma.
France's Emmanuel Macron yesterday said he had "proof" that the regime of Syrian President Bashar al-Assad had used chemical weapons, and would respond to it "at a time of our choosing."
One day after warning regime-backer Russia that "missiles will be coming" to Syria, Trump in another early morning tweet storm wrote: "Never said when an attack on Syria would take place. Could be very soon or not so soon at all!"
British Prime Minister Theresa May was due to hold an emergency cabinet meeting amid speculation she will support US action against the Syrian regime.
Germany's Angela Merkel said it was "obvious" that Syria hadn't eradicated its chemical arsenal as it had earlier claimed.
Meanwhile opponents of unilateral US action called an emergency closed-door meeting of the UN Security Council for Thursday.
The White House has said that Trump holds Assad's regime and its military backers Russia responsible for an alleged attack on Douma on Saturday, which rescue workers said killed more than 40 people.
Trump on Wednesday slammed Russia for its military alliance with Assad, saying it should not "be partners with a Gas Killing Animal who kills his people and enjoys it."
US officials have refused to rule out direct military engagement with Russia, with the White House saying that "all options are on the table."
Defense Secretary Jim Mattis said Wednesday the Pentagon was ready to provide options for a Syria strike but that the US and its allies were still "assessing the intelligence" on the suspected chemical attack.
A special hotline for the US and Russian militaries to communicate about operations in Syria is active and being used by both sides, Moscow said yesterday.
Moscow called on the West to "seriously consider" the consequences of threats against Syria.
"We call upon... members of the international community to seriously consider the possible consequences of such accusations, threats and especially action (against Syria)," Russian foreign ministry spokeswoman Maria Zakharova said.
Assad yesterday warned that threats of Western military action "will only contribute to further destabilization in the region."
Russia has warned the United States against carrying out a "military intervention on fabricated pretexts," and has accused the White Helmets civil defense organization in Syria of staging a fake chemical weapons attack in Douma.
The Russian army declared early Thursday that the Syrian state flag was flying in Douma, where the alleged chemical attack took place.
Moscow said this a "significant event in the history of Syria," meaning that the whole of Eastern Ghouta had come under government forces' control.
United Nations Secretary General Antonio Guterres on Wednesday said he had met with ambassadors from the five permanent members including Russia and the United States, and "stressed the need to avoid the situation spiralling out of control."
At the UN Security Council, Moscow and Washington have so far vetoed each other's motions to set up an international investigation into chemical weapons use.
Macron has insisted he does "not want an escalation" and that any response would focus on Syria's chemical capabilities, not on allies of the regime.
Turkish President Recep Tayyip Erdogan has vowed those behind the killings of civilians would pay a "heavy price", after the foreign ministry said there was a "strong suspicion" Assad's regime was responsible.
Erdogan yesterday said Turkey was worried by the "arm wrestling" of world powers over Syria.
Syria said it had invited the Organization for the Prohibition of Chemical Weapons, which has blamed the regime for previous attacks, to visit Douma.
Late yesterday, Syria's UN ambassador Bashar Jaafari said that two groups of experts from the OPCW will arrive in Syria today to investigate allegations of chemical weapons use.
Syria's White Helmets said the attack took place late on Saturday using "poisonous chlorine gas".
"More than 500 cases.. were brought to local medical centers with symptoms indicative of exposure to a chemical agent" including "respiratory distress" and foaming at the mouth, the Syrian American Medical Society (SAMS) and the White Helmets said in a joint statement.
Damascus agreed to hand over its chemical arsenal in 2013, narrowly avoiding American and French air strikes in retaliation for a suspected sarin attack.