President Donald Trump on Saturday described the alleged chemical attacks in Syria as the “crimes of a monster” as the US launched precision strikes on the war-torn nation jointly with the UK and France.

Trump ordered the launch of air strikes on Syria and accused President Bashar al-Assad of “barbarism and brutality”.

The US president claimed that the joint action was meant to establish a “strong deterrent” against the production, spread, and use of chemical weapons. Trump said he has ordered “precision strikes” against Syria, where dozens of people were killed last weekend in a suspected toxic gas attack on Douma, the largest town in a former rebel stronghold outside Damascus.

“These are not the actions of a man; they are crimes of a monster instead,” Trump said in an address to the nation.

Trump said the US would maintain pressure on Syria until the Assad regime suspends use of chemical weapons.

“America does not seek an indefinite presence in Syria,” he said, thanking the UK and France for joining the US in its fight against the Syrian regime.

“Today, the nations of Britain, France, and the United States of America have marshaled their righteous power against barbarism and brutality,” Trump said.

He attacked the Assad regime for “deploying chemical weapons to slaughter innocent civilians”, referring to the alleged atrocity in Douma last Saturday. “This massacre was a significant escalation in a pattern of chemical weapons use by that very terrible regime,” Trump alleged.

The US president sought to bring back the vestiges of World War I, after which civilised nations joined together to ban chemical warfare.

He noted that chemical weapons not only inflict gruesome suffering but also even small amounts of them can unleash widespread devastation.

“The purpose of our actions is to establish a strong deterrent against the production, spread, and use of chemical weapons. Establishing this deterrent is a vital national security interest of the US,” he said.

“The combined American, British, and French response to these atrocities will integrate all instruments of our national power — military, economic, and diplomatic. We are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents,” he said.