(ABC NEWS) -- President Donald Trump said that the attack in Syria on Tuesday "crossed a lot of lines for me," but did not specify how he would respond to the incident.

His comments came during a joint press conference with Jordanian King Abdullah II that began with Trump condemning the "heinous actions" that left at least 72 people dead.

Trump was asked if the attacks crossed a red line for him, a reference to former President Barack Obama's 2012 threat that the use of chemical weapons would be seen as doing so.

"It crossed a lot of lines for me. When you kill innocent children, innocent babies, little babies, with a chemical gas that is so lethal, people were shocked to hear what gas it was, that crosses many, many lines, beyond a red line, many, many lines," he said.

Later, when a reporter noted he seemed reluctant to get involved in the incident, Trump said, "I watched past administrations say we will attack at such and such a day at such and such an hour. ... I'm not saying I'm doing anything one way or the other."

Trump initially released a statement on Tuesday saying the acts were "a consequence of the past administration’s weakness and irresolution," but today he noted that as president he now has to take responsibility moving forward.

"I think the Obama administration had a responsibility to solve the crisis a long time ago. And when he didn't cross that line in making the threat, I think that set us back a long ways not only in Syria, but in many other parts of the world because it was a blank threat. I think it was something that was not one of our better days as a country."

He added: "I now have responsibility and I will have that responsibility and carry it very proudly."

Trump said that he is open to changing his stance on issues, and the incident in Syria is one example of how current events have prompted a shift.

"I like to think of myself as a very flexible person. I don't have to have one specific way, and if the world changes, I go the same way," Trump said. "It's already happened, that my attitude towards Syria and Assad has changed very much."

Trump also praised Jordan's efforts in the fight against ISIS.

"The Middle East and the entire world is faced with one of its gravest threats in many, many years. Since the earliest days of the campaign against ISIS, Jordan has been a staunch ally and partner, and we thank you for that," Trump said later in his remarks.

"In King Abdullah, America is blessed with a thoughtful and determined partner. He's a man who has spent years commanding his country's special forces. He really knows what is being a soldier is, that, I can tell you. And he knows how to fight," he said.