By working with two other allies, and spending several days consulting with military commanders and leaders in Europe and the Middle East, Trump's approach differed from a unilateral USA missile attack against Syria nearly exactly a year ago in the aftermath of another chemical attack blamed on Assad's forces.
British Prime Minister Theresa May won backing from her senior ministers on Thursday to take unspecified action with the United States and France to deter further use of chemical weapons by Syria.
Nebenzia told reporters after a closed emergency meeting of the U.N. Security Council on Thursday that "the danger of escalation is higher than simply Syria, because our military is there on the invitation of the Syrian government".
The combined decision by the United States and its allies to strike Syria comes after Russian Defence Ministry spokesperson Major-General Igor Konashenkov presented evidence claiming that last Saturday's alleged chemical attack in Douma was orchestrated.
In the wake of last weekend's gruesome attack, some USA officials advocated a larger, and therefore riskier, strike than the limited action Trump ordered in April 2017, also in response to suspected chemical weapons use.
The strikes were a response to a suspected chemical weapons attack on the Syrian town of Douma last weekend which killed dozens of civilians.
The Kremlin said Mr Putin yesterday warned his French counterpart during a telephone call against any "dangerous actions" in Syria.
The WHO cautioned that it has no formal role in forensic inquiries into the use of chemical weapons.
Konashenkov said that "powerful pressure from London was exerted on representatives of the so-called White Helmets to quickly stage the premeditated provocation". Not for decades, they said, had the United States and Russian Federation come so close to a direct military clash.
The US and its allies, Nebenzia alleged, are setting the stage to "unleash a military scenario against Syria".
The Russian military has also made belligerent statements, but Putin himself and the Moscow foreign ministry have instead played the injured party, demanding proof of Assad's culpability.
"It's not satisfactory that these kinds of actions are now happening on a regular basis, where we can't get absolutely watertight proof publicly available in advance, rather than being told to trust the Government - and then an action like this happens".
Trump's warlike tweets came in response to a warning from Russia's ambassador to Beirut, who took to a television network run by the armed group Hezbollah to declare that any USA missiles would be shot down "as well as the sources they were fired from".
Vladimir Shamanov, who chairs the defense committee of the lower house, said the vessels had departed the Mediterranean base for their own safety - "normal practice" when there were threats of attack.
In the UK, Cabinet ministers said that it was "highly likely" the Assad regime was responsible for the attack and said the use of chemical weapons must not "go unchallenged".
Inspectors from the global Organization for the Prohibition of Chemical Weapons were expected to make their initial foray Saturday to Douma.
During his meeting with Trump and the Chairman of the Joint Chiefs of Staff Joe Dunford, Mattis pushed for more evidence of the Assad regime's culpability for the attack, to bolster the case for air strikes, The New York Times reported. Clearly, we are going to deal with a lot of pressure, but war is a unsafe thing for the Americans in the first place. It also said Russian officers found no patients with chemical attack symptoms at a local hospital, and no indication of any burials of victims.
As fears of a Russia-West military confrontation mounted, French President Emmanuel Macron expressed his "deep concerns" over the situation in Syria in a phone call with Russian President Vladimir Putin. Russian Federation needs us to help with their economy, something that would be very easy to do, and we need all nations to work together.
Western officials believe chlorine was used in Saturday's attack on Douma, the main city in the longtime rebel bastion of Eastern Ghouta, where the British government now estimates 75 people were killed.
Kim Jong Un fetes Chinese art troupe in meeting
On Saturday, the National Ballet of China staged a performance of "Giselle" at the Mansudae Art Theatre in Pyongyang. Song returned to Beijing without meeting Kim.