The Russian military claimed Syrian air defense systems had intercepted 71 Western missiles, though the Pentagon disputed that.
Japan's support for the "resolve" behind the reasoning for the strikes echoes its response to a USA air strike on a Syrian airbase in April previous year in retaliation for another alleged chemical attack.
The April 7 attack in the rebel-held town of Douma killed at least 70 residents and injured hundreds more.
According to the Russian Defense Ministry, the missile strike against Syria's military and civilian infrastructures was carried out by United States planes and naval ships in cooperation with British and French air forces between 03:42 and 05:10 Moscow time on Saturday.
Nonetheless, according to initial reports, the strikes were the biggest ever by the three Western powers against Syria in the country's seven-year-old conflict, which has pitted the U.S. and its allies against Russian Federation.
A plane preparing to take off as part of the joint airstrike operation by the British, French and USA militaries in Syria, is seen in this picture obtained April 14, 2018, via social media.
On the other hand, Syrian Foreign Ministry denounced the attack, stressing it will not affect determination of the Syrian people and army to defend their country.
In response, US President Donald Trump called Syrian President Bashar al-Assad "a gas killing animal".
Mattis, who U.S. officials said had earlier warned in internal debates against too large an attack that would risk confrontation with Russian Federation, described the strikes as a "one time shot" to dissuade Assad from "doing this again".
"We are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents", President Trump said in announcing the strikes from the White House.
The foreign ministry said earlier on Saturday that the US -led strikes would only "lead to inflaming tensions in the world" and threaten global security.
U.S. Joint Chiefs of Staff Chairman Gen. Joseph Dunford said the deconfliction line with Russian Federation was "active" this week.
General Joseph Dunford, Washington's top general, said the precision strikes hit a scientific research center near Damascus, a storage facility and command post also near the capital and a chemical weapons storage facility near Homs.
Mr Trump said that the USA and its allies "are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents".
Richard Becker of the US-based anti-war ANSWER Coalition told RT he believes Britain and France are becoming "old colonizers of the Middle East back again, and the United States is more of a new colonizer".
However, Mr Mattis threatened a sustained campaign if regime forces use chemical weapons in the war. "Thank you to France and the United Kingdom for their wisdom and the power of their fine Military", Trump tweeted early Saturday.
White, the Defence Department spokeswoman, said the strikes did not "represent a change in US policy or an attempt to depose the Syrian regime".
"We understand this action to be a measure taken to prevent the situation worsening further", he said.
A photo released on April 14, 2018 on the Twitter page of Hezbollah's "Central War Media" account shows night footage of flares above Damascus seen through a night-vision device as Western strikes reportedly hit Syrian military bases and chemical research centres in and around Syria's capital.
Editor's note: This UpFront debate was recorded shortly before the US-led attack on chemical weapon sites in Syria. But it did nothing to target the Syrian Government's chemical weapons stockpile.
Mr Dunford stressed that Russian Federation was not warned of the attack, nor did the USA or any of its allies co-ordinate with Russian Federation.
Donald Tusk, President of the European Council, said the European Union "will stand with our allies on the side of justice".
For their part, British Prime Minister Theresa May and French President Emmanuel Macron announced the participation of their countries in the aggression.
In his nationwide address, Trump stressed that he has no interest in a longtime fight with Syria.
The US has about 2,000 troops on the ground in Syria as advisers to a makeshift group of anti-Daesh fighters known as the Syrian Democratic Forces.
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