While Syria’s foreign minister Walid Muallem has denied the use of chemical weapons in Tuesday’s attack, the United States President Donald Trump has described the chemical attack that killed more than 86 people in Syria as a “heinous” act that had changed his views on Syrian President Bashar al-Assad.

Speaking at a White House press conference, Trump said the attack had “crossed a lot of lines for me” and that it could not be tolerated.

Trump did not offer any details of how US strategy on Syria would change, and he did not directly criticise Russia, which has stood by Assad in the face of worldwide condemnation of the attack. But Trump said details of the attack had affected him profoundly.

“Wednesday’s chemical attack, a chemical attack that was so horrific in Syria against innocent people, including women, small children and even beautiful little babies, their deaths were an affront to humanity,” Trump said.

“These heinous actions by the Assad regime cannot be tolerated. The United States stands with our allies across the globe to condemn this horrific attack and all other horrific attacks, for that matter,” he said.

Asked about the first statement released by the White House after the attack on Wednesday, which blamed the attack in part on the policies of former President Barack Obama, Trump said: “I now have responsibility, and I will have that responsibility and carry it very proudly.”

Trump said that Obama, who in 2012 said the use of chemical weapons by the Syrian regime would be a “red line,” had missed a “great opportunity” to deal with Assad. “It is now my responsibility. It was a great opportunity missed,” Trump said.

He maintained that Obama’s failure to enforce his red line threat was a blank threat (that) set us back a long ways, not only in Syria but in many other parts of the world,” CNN reported.Trump also left the door open to new action in Syria.