Syrian government forces were on high alert and taking precautionary measures at military positions across the country.
"We are studying the situation extremely closely, we are meeting with our military and everybody else and we'll be making some major decisions over the next 24 to 48 hours".
Vladimir Shamanov, a retired general who heads the defense affairs committee in the lower house of parliament, said in televised remarks Tuesday that a US strike in Syria could hurt Russian servicemen and trigger Russian retaliation. Trump gave no hints about potential USA action, but al-Thani told reporters, "We can not tolerate, with a war criminal" like Assad.
President Trump is canceling this weekend's South American trip to Peru and Colombia because of the crisis over Syria, the White House said Tuesday.
"We are looking into the attack at this point", he said, adding that the photos of the incident are "horrible".
British Prime Minister Theresa May and U.S. President Donald Trump have said the world must act to ensure those behind a suspected chemical attack in Syria are held to account, as the United States considers a multinational military response.
"And so, working with our allies and our partners from North Atlantic Treaty Organisation to Qatar and elsewhere, we are going to address this issue", Mattis said in brief remarks to reporters as he began a meeting with the emir of Qatar. "All options are on the table, but I'm not going to get ahead of what the President may or may not do".
Meanwhile, a US official on Monday confirmed to Fox News that Israel conducted an airstrike on a Bashar al-Assad air base in Syria on Sunday night. Officials said the jamming operation began several weeks ago.
In his tweets Sunday, Trump called Assad an "animal" and delivered a rare personal criticism of Russian President Vladimir Putin for supporting him. He added that the use of nuclear weapons is "unlikely". "Russian Federation wants to undermine our interests at every turn".
Attacking Russia for its "repeated vetoes" at the UN, Mrs May said they had "enabled these rules to be broken. and removed mechanisms that allow us to investigate" chemical weapons attacks in Syria.
If the United States proposal is put to a vote, it would likely be vetoed by Russian Federation.
"This resolution is the bare minimum that the council can do to respond to the attack", U.S. Ambassador Nikki Haley told the council before the vote.
Russia's United Nations representative Vassily Nebenzia, however, told the Security Council that images of the dead in Douma were staged and "fake news".
French President Emmanuel Macron said on Tuesday that any strikes would not target the Syrian government's allies or anybody in particular, but would be aimed at the Syrian government's chemical facilities.
Earlier Monday, Defense Secretary Jim Mattis took aim at Russian Federation for what he suggested was its failure to ensure the elimination of Syria's chemical weapons arsenal.
Top U.S. military chiefs reportedly advised the president that their forces need to remain in Syria to prevent an ISIS resurgence.
Shamanov emphasized that a retaliatory Russian strike could target US navy ships and aircraft.
He said that Russian Federation has "the necessary means for that and the Americans and their allies know that quite well".
Rebels blamed the government, which denies any involvement, and U.S. President Donald Trump pledged to take swift action.
A European source said European governments were waiting for the OPCW to carry out its investigation and for more solid forensic evidence from the attack to emerge. Vice President Mike Pence will attend the 8th Summit of the Americas in his place, the White House said in a press briefing Tuesday.
Turkish President Recep Tayyip Erdogan says his country will hand over control of the strategic town of Afrin - which Turkish troops seized from Syrian Kurdish forces last month - to the people of Afrin "when the time is right". Monday was the first day on the job for his new national security adviser, John Bolton, who has previously advocated military action against Syria. If Trump decides to proceed quickly, the most likely partner would be France rather than Britain, because of concerns about obtaining permission from Parliament, said the official, who wasn't authorized to discuss the planning publicly and requested anonymity.
In his Oval Office appearance with the emir of Qatar, Mr. Trump made no mention of his intentions in Syria.
So Trump is staying put, the White House says. "We can not tolerate with a war criminal", he said, adding, "This matter should end immediately". "This matter should end immediately".
The U.S. military has a wide range of warplanes and other capabilities in the Middle East. The Navy does not now have a carrier in the Persian Gulf. Ali Akbar Velayati, an aide to Iran's supreme leader, spoke upon arrival in the Syrian capital on Tuesday.
Reports suggested more than 500 people, mostly women and children, were brought to medical centres with difficulty breathing, foaming at the mouth, and burning sensations in the eyes.