Damascus: The global chemical watchdog said Tuesday it will soon deploy a team to the site of an alleged toxic attack in Syria, as the regime in Damascus was on high alert after Western threats of a forceful response.
Warnings from US President Donald Trump there would be a "big price to pay" for the alleged attack have raised the spectre of an American strike on Syria, setting up a potential confrontation with regime backer Russia.
Moscow, which has troops on the ground in Syria, has already warned that US military action would be "very, very dangerous".
After threatening a decision within days, Trump on Tuesday abruptly cancelled his first trip to Latin America in order to oversee Syria developments.
Potentially looking to head off Western military strikes, Syria's foreign ministry said it had invited the Organisation for the Prohibition of Chemical Weapons (OPCW) to visit the site of the alleged attack.
"Syria is ready to provide all necessary assistance to the mission," it said.
Several hours after the invitation, the OPCW said it will "shortly" deploy a fact-finding team to the rebel-held Syrian town of Douma to probe the alleged poison gas attack.
In anticipation for a potential strike, Syria's military forces across the country were also simultaneously mobilising, according to a war monitor.
"At midnight, the army command put all military positions on alert, including airports and all bases, for a period of 72 hours," the Syrian Observatory for Human Rights said Tuesday.
The Britain-based war monitor, which relies on sources across Syria, said units were preparing themselves for rapid deployment.
Even residents of Damascus were bracing themselves.
"I have lived through seven American presidents, but Trump is the craziest and his administration is unbalanced," said Abu Fadi, a retired resident.
"I think his threats are to be feared, and we should take them seriously."
In 2017, Trump launched a cruise missile strike against a Syrian air base after a sarin attack the UN later pinned on President Bashar Al Assad.
Syria's government has repeatedly denied accusations of using toxic weapons including chlorine and sarin throughout the country's seven-year war.
First responders in rebel-held Douma say more than 40 people died on Saturday after the suspected gas attack, which left people wheezing, with discoloured skin, and foaming at the mouth.
The town has been heavily bombed by Syria and Russia and cut off by the regime, making it extremely difficult for media including AFP to independently verify the claims.
Reaching sources inside the town is complicated by their patchy access to lines of communication.
United Nations chief Antonio Guterres said Tuesday the OPCW should be granted unfettered access to investigate the reports.
The US has asked the UN Security Council to vote Tuesday on its proposal to set up an inquiry to investigate chemical weapons attacks in Syria, but the measure is likely to face a veto from Russia, diplomats said.
Moscow said it was also planning to propose its own "transparent and honest" probe with the OPCW's involvement at the meeting.
It said its own investigators already entered Douma and found no trace of chemical use.
"Fabrications and false stories are being used to find some pretext for the use of military force," deputy foreign minister Mikhail Bogdanov said.
At a Security Council meeting Monday US Ambassador Nikki Haley said the "world must see justice done".
Syria's UN ambassador Bashar Al Jaafari responded by accusing Western powers of staging such attacks to justify military action against Damascus.
Jaafari said Washington, Paris, and others were falsely accusing his government of chemical use "in order to pave the way for an attack on Syria like the US and Britain's criminal aggression against Iraq in 2003."
Damascus narrowly avoided American and French air strikes in 2013 in retaliation for a suspected sarin attack by agreeing to hand over its chemical arsenal.
That attack, which killed hundreds in the deadliest use of toxic gas, also took place in Eastern Ghouta, the suburb outside the Syrian capital where Douma is located.
Trump has repeatedly threatened to respond "forcefully" to the most recent allegations in Douma, saying the US had "a lot of options militarily" and would decide in the coming days.
Washington has been co-ordinating closely with Paris, which said Tuesday it would retaliate against Assad if evidence emerged the Syrian leader had crossed a "red line" by using toxic gas in Douma.
Douma is the last rebel-controlled area in Ghouta, the opposition's former stronghold on the edges of Damascus.
Since February 18, Assad has captured most of Ghouta with a ferocious military assault and two negotiated rebel withdrawals.
A third deal was reached for Douma just hours after the reported chemical attack, and a 65-bus convoy of rebels and civilians was evacuated from the town overnight.
Syria's conflict erupted with anti-Assad protests in 2011 but has since evolved into a complex war that has killed 350,000 people.