President Donald Trump has canceled a foreign trip to manage the crisis, which is testing his vow a year ago to stop Syrian President Bashar Assad from using chemical weapons against his own people. He suggested Syria's main military ally, Russia, would "pay a price".
Calling for Mr Trump to launch strikes against the Syrian regime, Mr Rasmussen said it would be "extremely important" for the United Kingdom to join the USA in any action and claimed "military pressure can facilitate political and diplomatic solutions" in the Syria's long conflict. The evacuation deal restores Assad's control over the entire eastern Ghouta - formerly the biggest rebel bastion near Damascus. When Trump ordered airstrikes past year after a chemical weapons attack, it was a response to the use of sarin gas, which is banned by the Chemical Weapons Convention that Syria has signed.
The Sound and Picture Organization, an activist collective in eastern Syria, said that Iranian fighters and members of Lebanon's Hezbollah group have evacuated their positions in the Boukamal area, near the Iraqi border, which was recently retaken from the Islamic State group.
The punitive raid did not draw USA forces any deeper into Syria's civil war, nor did it dissuade Syria or its Russian and Iranian backers from pursuing their campaign against rebel groups.
President says all options are on the table as he weighs USA retaliation for suspected gas attack in Syria; Kristin Fisher reports from Washington. "Nobody has invested you with the authority to act as gendarmes, policemen of the world. we call on you to return to the legal fold", Ambassador Vassily Nebenzia said.
Russian Federation on Tuesday vetoed a USA -drafted United Nations Security Council resolution to set up an expert body that would assign blame for chemical attacks in Syria.
If the U.S. proposal is put to a vote, it would likely be vetoed by Russian Federation.
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.
"This is basically a diplomatic set-up", said Richard Gowan, a United Nations expert at the European Council on Foreign Relations.
One senior Tory said he had been disappointed by the PM's response - saying "she should be all over this, and leading from the front".
One US official told CNN that the White House will most likely coordinate with France on a potential response, as there are concerns Prime Minister May wouldn't receive approval from the UK Parliament for strikes.
Trump is the 45th President of the United States.
The ministers "noted that worldwide investigators mandated by the UN Security Council had found the Assad regime responsible for using poison gas in at least four separate attacks since 2014 and agreed that those responsible for this attack must be held to account", the statement added.
Russian UN Ambassador Vassily Nebenzia accused the United States, France and Britain of stoking worldwide tensions by engaging in a "confrontational policy against Russia and Syria".
"Russia is being unpardonably threatened", Nebenzia told the meeting. "The tone with which this is being done has gone beyond the threshold of what is acceptable, even during the Cold War".
Calling the attack "horrible", Trump has pledged to respond "forcefully".
Trump said, however, that Washington was "getting more clarity" on who was responsible. He also reaffirmed his support for an OPCW investigation.
Volunteer rescue service The White Helmets, which also has links to opposition forces, said numerous victims were women and children.
Last month, a United Nations commission of inquiry released a report accusing the regime of committing war crimes in Eastern Ghouta, including the use of chemical weapons against civilians.
Gen. Yuri Yevtushenko was quoted by Russian news agencies Sunday as saying Russia was prepared to send specialists to Douma to "confirm the fabricated nature" of the reports.
His comments, reported by the state-run Anadolu Agency on Tuesday, were in response to Russia's Foreign Minister Sergey Lavrov who said Monday that Russian Federation expects Turkey to bring Afrin under the control of the Syrian government.
"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".
A group of detainees arrived in Damascus overnight Monday to Tuesday after being freed by Jaish al-Islam, state news agency SANA said.