Donald Trump has called on "all civilised nations to end the slaughter and bloodshed in Syria" after he ordered a military strike on the country.
The US leader said he the targeted airfield was the one from which a chemical attack was launched on Syrian civilians.
Speaking at his Mar a Lago resort in Florida, he added that it was in the vital national security interests of the US to prevent and deter the spread and use of chemical weapons.
There was "no dispute that Syria used banned chemical weapons," he said.
Mr Trump had said earlier that the deaths of more than 70 people in Khan Sheikhoun had changed his opinion of Syrian President Bashar al-Assad, whom US intelligence says is responsible for the attack.
"Using a deadly nerve agent, Assad choked out the lives of hopeless men, women, and children," he said. "It was a slow and brutal death for so many. Even beautiful babies were cruelly murdered in this very barbaric attack. No child of god should ever suffer such horror."
He added that "years of previous attempts at changing Assad's behaviour have all failed and failed very dramatically."
He continued: "As a result, the refugee crisis continues, and the region continues to destablise, threatening the US and its allies. Tonight I call on all civilised nations in seeking to end the slaughter and bloodshed in Syria and also to end terrorism of all kinds and all types."
The Syrian government, and its Russian allies, have denied that the regime possesses chemical weapons stocks, which were handed over to the Organisation for the Prevention of Chemical Weapons (OPCW) after a deadly sarin gas incident in rebel-held Ghouta in 2013.
The strikes sent "an important message", according to Republican senators John McCain and Lindsey Graham, who have long pushed for stronger action against Syria, have issued a joint statement.
They saluted the US forces carrying out the strike, adding: "They have sent an important message the United States will no longer stand idly by as Assad, aided and abetted by Putin’s Russia, slaughters innocent Syrians with chemical weapons and barrel bombs".
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