In Moscow, a senior Russian lawmaker said his country is willing to help arrange a visit this week for experts from the worldwide chemical weapons watchdog to the site of a suspected poison gas attack in Syria.
On Wednesday, Defence Secretary James Mattis said the USA was still assessing the chemical attack and that the United States military stood ready "to provide military options if they are appropriate as the president determines". "At the President's request, the Vice President will travel in his stead".
"The latest attack joins a long series of similar attacks using chemical weapons perpetrated by the regime since Assad undertook to disarm from such weapons".
He said that after conferring with his military advisers, he would soon decide on how to respond, and against whom.
Meanwhile on the ground, thousands of militants and their families arrived in rebel-held northwestern Syria after surrendering Douma to government forces.
Vassily Nebenzia said U.S. attacks on Syria "could lead to grave repercussions" during heated exchanges at the UN Security Council.
But whether a team would try to get there was unclear.
But Western leaders say they have agreed to work together to target those responsible for the attack in Douma.
On April 10, Russia's UN ambassador pleaded with the United States not to stage a military strike against Syria after competing US and Russian calls for investigations into the suspected attack in Douma failed to win approval in the UN Security Council.
The Russian Ambassador Vassily Nebenzia hit back at the United States accusing them of planting the resolution as a "pretext" to justify action against Syria.
U.S. Defense Secretary Jim Mattis on Monday accused Russian Federation of falling short on its obligations to ensure that Syria abandoned its chemical weapons capabilities. He said that Russian Federation uses the veto to protect global law and peace, while stating that the United States is willing to take unilateral actions, regardless of any decision of the Security Council.More news: Israel strikes several Hamas targets in Gaza
News of the OPCW mission to Douma also came as the UN Security Council was due to vote later Tuesday on rival USA and Russian draft resolutions in response to the alleged attack.
Tuesday's veto is Russia's twelfth of council resolutions seeking to hold the Assad regime accountable for rights violations.
Trump says on Twitter Wednesday: "Russia vows to shoot down any and all missiles fired at Syria". "Either way, the United States will respond". As a response, the cruise missile attack was order on Syrian air base by President Trump.
Trump spoke by phone with British Prime Minister Theresa May.
"The U.S. ordering a military strike against another country is pretty serious business", Singh said.
U.S. ambassador to the United Nations Nikki Haley said before the vote that her delegation had tried hard to incorporate Russian proposals in the draft that would not compromise the impartiality of investigation. "The tone with which this is being done has gone beyond the threshold of what is acceptable, even during the Cold War". Moscow has cautioned the US not to launch a military attack.
Trump said, however, that Washington was "getting more clarity" on who was responsible.
The opposition blamed President Bashar Assad's forces for the attack, accusations the government and its Russian backers strongly deny.
Syria has denied that it used poison gas.
Syrian Army soldiers on the eastern outskirts of Douma.
The organization is now in the process of gathering information from all available resources in an effort to determine whether chemical weapons were used, and if so - by who.
Following the alleged attack, Syria and Russian Federation reached an evacuation deal with the Jaish al-Islam rebels, who up until now have been holding Douma.