The foreign ministry also called for an investigation by the Organisation for the Prohibition of Chemical Weapons (OPCW) and said it expected the worldwide community to condemn the attack. The Syrian state denied government forces had launched any chemical assault.
Turkey and Russian Federation have been on opposing sides of the conflict in Syria, as Moscow is the chief ally of the Bashar al-Assad regime while Ankara backs rebels seeking to oust him.
Trump threatened action, although it was unclear what he had in mind.
"It is a matter of grave concern that chemical weapons continue to be used, especially on civilians". "Area of atrocity is in lockdown and encircled by Syrian Army, making it completely inaccessible to outside world".
The European Union said "the evidence points towards yet another chemical attack by the regime". "His calculation is based on whether it will help his chances in achieving gains on the ground, or punishing the rebels", he said.
British Prime Minister Teresa May called the attack "barbaric", saying during a visit to Denmark that "If they are found to be responsible, the regime and its backers, including Russian Federation, must be held to account". Late Saturday (Sunday NZT), the State Department singled out both governments, saying they "must be held accountable".
"I have said in the past and I say again, there is a cruel genocide happening in Syria against women and children with weapons of mass destruction", Yosef said on Sunday morning. His advisers have urged him to wait to ensure the militants are defeated and to prevent Assad's ally Iran from gaining a foothold.
Is Trump Withdrawing the US Troops?
Yet Turkey has worked closely in the last months with Russian Federation and Assad's other main ally, Iran, in what they call a bid to bring peace to Syria. "The question now is whether he will do anything about it", McCain said in a statement. When asked if the U.S. would respond in a similar way to this latest alleged chemical attack, White House adviser Tom Bossert told ABC television: "I wouldn't take anything off the table".
Graphic images showed people, including children, apparently dead and injured - some with some kind of spittle or foam in their mouths in makeshift medical centers.
The reports could not immediately be independently verified.
Israel has also struck inside Syria in recent years.
Medics said chlorine could be smelled on children who turned blue in the face as they gasped for breath.
The Observatory gave a higher death toll, saying at least 80 people were killed in Douma, including around 40 who died from suffocation.
A chemical attack in a Syrian rebel-held town has sparked widespread global outrage and revulsion.
Trump had a previously scheduled meeting at the White House on Monday with senior military leaders.
Bolton previous year praised Trump's missile response, though he has generally focused more on Iran as a bigger security threat.
- United Nations-OPCW Joint Investigative Mechanism in Syria is established to identify individuals or entities behind chemical weapons attacks. "These reports, if confirmed, are horrifying and demand an immediate response by the worldwide community", US State Department spokeswoman Heather Nauert said in a statement.
In an appearance on ABC's "This Week", Bossert said USA officials have examined photos and information about the incident in Douma, a Damascus suburb.
Trump's threat came exactly a year and a day after the U.S. army fired cruise missiles at a Syrian airbase in retaliation for a deadly sarin gas attack on the rebel-held town of Khan Sheikhoun.
Britain called for an investigation into what it said were the "deeply disturbing" reports, and Turkey, which has backed rebels against Assad, said it had a "strong suspicion" the Syrian president was to blame.
Medical relief organization SAMS said a chlorine bomb hit Douma hospital, killing six, and a second attack with "mixed agents", including nerve agents, had hit a nearby building.
The White House sharply rejected any suggestion that Trump's own words about pulling USA troops out of Syria had opened the door for the attack, which killed more than 40 people, including children.
It said the attack left people dead and wounded. "To me there's not much of a doubt, but the generals will figure it out", Trump said.
Douma is in the eastern Ghouta region near Damascus. They come at seminal junctures in the conflict, when Syrian government forces are on the verge of a significant strategic victory or advance against the alphabet soup of Salafi-jihadi groups that are operating in the country.
There was no immediate comment from the group.
The Army of Islam is holding thousands of people in the Tawba prison that they run inside Douma.
Cyber Monday 2017 – The top sellers in electronics this year
Apple’s 9.7-inch Wi-Fi enabled iPad Pro was also still a great seller thanks to massive price discounts from retailers. Microsoft dropped their game changing console update, the Microsoft Xbox One X with a 1TB hard drive and 4K compatibility.