Story highlights Trump describes Syria attack as "affront to humanity"

Tillerson calls on Russia to reconsider support for Assad

Washington (CNN) President Donald Trump has described the chemical attack that killed more than 70 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 criticize Russia, which has stood by Assad in the face of worldwide condemnation of the attack.

JUST WATCHED Syrian describes losing 25 relatives in attack Replay More Videos ... MUST WATCH Syrian describes losing 25 relatives in attack 02:15

But Trump said details of the attack had affected him profoundly. "Yesterday'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, speaking in the Rose Garden alongside Jordan's King Abdullah.

"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."