Pledging to coordinate action under the framework of the United Nations Security Council, they stressed "all responsibilities in this area must be clearly established".
In New York, the United Nations Security Council met after Washington urged the worldwide community to approve a probe into the alleged attack on rebel-held Douma that reportedly killed at least 40 people.
The line-up among the global parties involved in the Syrian conflict - France, Iraq, Lebanon, Russia, Saudi Arabia, Turkey, and the United States, as well as the Kurds - also bears on what happens next in Syria.
In an angry statement, he invited investigators from the Organisation for the Prohibition of Chemical Weapons (OPCW) to fly to Syria as soon as Tuesday, saying that Russian troops would escort them to the site of the alleged attack. "I think that it is outrageous to say that the president of the United States green-lit something as atrocious as the actions that have taken place over the last several days", she said. "Such claims and accusations [about chemical weapons use] by the Americans and some Western countries signal a new plot against the government and nation of Syria and is an excuse for military action against them", he said.
"If it's Russian Federation, if it's Syria, if it's Iran, if it's all of them together, we'll figure it out and we'll know the answers quite soon", he told reporters earlier on Monday.
The cause of the explosion was not immediately apparent, but the Britain-based Syrian Observatory for Human Rights said 13 people had been killed and another 80 wounded.
Mr Trump said the United States is still investigating the possible involvement of the Iranian and Russian governments in the apparent strike on Douma. The opposition's Syrian Civil Defense rescue organization said the victims appeared to have suffocated.
Donald Trump Sends Regrets & Sanders To WH Correspondents Dinner
Trump was mocked in 2011 by the then president Barack Obama and the comedian who turned up for the day - Seth Meyers. Considering Trump's current relationship with the free press, that likely won't come as much of a surprise.
The Trump Administration ordered a targeted air strike on a military base in Syria after a chemical weapons attack that took the lives of at least 90 in Syria a year ago.
Initial US assessments have been unable to determine conclusively what materials were used in the attack and could not say with certainty that Syrian President Bashar al-Assad's government forces were behind it. "More than 500 cases -the majority of whom are women and children- were brought to local medical centers with symptoms indicative of exposure to a chemical agent", SAMS said.
Since 2012, Israel has struck inside Syria more than 100 times, mostly targeting suspected weapons' convoys destined for the Lebanese militant group Hezbollah, which has been fighting alongside Syrian government forces.
Brand new National Security Adviser John Bolton reported to work at the White House Monday morning and was greeted with a giant crisis.
"We are quick to condemn chemical weapons in the Security Council, but then Russian Federation prevents any action, vetoing five resolutions on this issue alone".
Syria has denied it had anything to do with a chemical attack.
April 7, 2018: A suspected chemical attack kills at least 40 people in Douma.
"... If we decide to get tough with Putin, lots of scary rhetoric, they'll talk about nuclear war, but they would I think, avoid any confrontation in Syria with us".