President Trump condemned the horrific chemical attack in Syria that has been blamed on its president, Bashar Assad, signaling a shift in Trump's approach toward the country's controversial leader — but didn't elaborate on how the U.S. would respond.

"It crossed a lot of lines for me," the president said during a Rose Garden news conference on Wednesday with Jordan's King Abdullah. "When you kill innocent children, innocent babies, little babies, with a chemical gas that is so lethal that people were shocked to hear what gas it was, that crosses many, many lines, beyond a red line, many many lines."

Trump doubled down on his criticism of the Obama administration's approach toward Syria, but he said that the attack, which has killed at least 72 people, "had a big impact on me" and has changed his approach toward the country.

"It's very, very possible that it's already happened, that my attitude toward Syria and Assad has changed very much," Trump said.

As NPR's Tamara Keith reported Tuesday, Trump's blaming former President Barack Obama for not acting after Assad crossed the "red line" after chemical weapons were first used was at odds with what Trump has said in the past, when he argued the U.S. should not get involved in the conflict.

"The world is a mess. I inherited a mess," Trump said Wednesday, reiterating his belief that he wished the administration of George W. Bush had not gotten involved in the Middle East with its invasion of Iraq.

"I think the Obama administration had a responsibility to solve the crisis a long time ago," Trump said of his predecessor's approach to the Syrian regime. "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."

But for the first time he seemed to signal that the U.S. could act against the atrocities, a departure from previous statements from the White House suggesting that ousting Assad was not a foreign policy priority and should instead be left up to the Syrian people.

Still, when pressed on how he would respond, Trump was coy and reiterated he didn't want to show his hand and would remain flexible.

"I now have responsibility, and I will have that responsibility and carry it very proudly," Trump said.

United Nations Ambassador Nikki Haley also suggested Wednesday that there could be U.S. intervention in Syria's ongoing civil war, strongly condemning not only the attacks but also blaming Russia for its support of the Assad regime.

"How many more children have to die before Russia cares?" Haley said, holding up photos of the young victims.

Trump has repeatedly praised Russian President Vladimir Putin, signaling a willingness to work with Russia to combat terrorism amid ongoing investigations into Russian efforts to influence the U.S. election last year and possible ties between Trump's presidential campaign and that country.

In an interview with the New York Times before the news conference, though, Trump did begin to cast blame toward Putin in another shift.

"I think it's a very sad day for Russia because they're aligned, and in this case, all information points to Syria that they did this," the president told the Times. "Why they did this, who knows? That's a level, first of all, they weren't supposed to have this."