WASHINGTON — President Trump said on Wednesday that this week’s devastating chemical weapons attack in Syria had changed his view of the brutal civil war in that country, though he declined to say how the United States would respond.
Mr. Trump said the images of death inside Syria in the aftermath of the chemical attacks “crosses many lines, beyond a red line, many many lines.” And he said that the death of “innocent children, innocent babies, little babies” has made him reassess the situation and Syria’s president, Bashar al-Assad.
“It’s very, very possible, and I will tell you it has already happened, that my attitude toward Syria and Assad, has changed very much,” Mr. Trump said as he stood next to King Abdullah of Jordan in the Rose Garden for a news conference with reporters.
Before the chemical attack, Mr. Trump’s administration had repeatedly said it did not intend to pursue the ouster of Mr. Assad. As recently as Tuesday, Mr. Trump’s spokesman said doing so would be “silly” in the face of the political realities in the country.
But Mr. Trump on Wednesday appeared to hint at a shift in that policy, though he offered only vague assertions that the aftermath of the chemical attack is “unacceptable” to him. Pressed on what his policy will be, Mr. Trump said it would be unwise to reveal any plans his administration might have.
A shift could suggest that Mr. Trump is considering military action through aircraft or missile strikes, much the way that former President Barack Obama debated — and ultimately rejected — options in the wake of a similar chemical attack by the Syrian government in 2013.
“I’m not saying I’m doing anything one way or the other,” Mr. Trump said, telling the reporter who asked the question: “But I’m certainly not going to be telling you, as much as I respect you.”
Mr. Trump on Wednesday repeated his belief that Mr. Obama bears blame for the chemical attacks because he declared that the use of chemical weapons by Syria would “cross a red line” and then declined to follow up on that threat by using military force.
“I think the Obama administration had a great opportunity to solve this crisis,” Mr. Trump said. “When he didn’t cross that line, after making the threat, I think that set us back a long ways. It was a blank threat.”
At the United Nations on Wednesday, the American ambassador, Nikki R. Haley, used her remarks at an emergency session to blame Russia for blocking a robust response to the chemical weapons attack.
The United States, France and Britain have accused the Syrian government of being responsible for the attack and have bitterly criticized Russia — Syria’s main ally in the six-year-old war — for objecting to a resolution condemning the attack.
Russia has said insurgents may have been responsible or the attack may have been fabricated to embarrass Mr. Assad.
“Time and time again Russia uses the same false narrative to deflect attention from their allies in Damascus,” Ms. Haley said. “How many more children have to die before Russia cares?”
She closed her remarks with an ominous warning. “When the United Nations consistently fails in its duty to act collectively, there are times in the life of states that we are compelled to take our own action,” she said. “For the sake of the victims, I hope the rest of the council is finally willing to do the same.”
Mr. Trump pledged to work with Jordan and other allies in the Middle East to defeat the Islamic State.
“We are both leaders on that,” Mr. Trump said, adding that “it will be a shorter fight than a lot of people are thinking about, believe me.”
Mr. Trump called the king a “tireless advocate” for peace in the Middle East and said he hoped that the two countries could work with Israelis and Palestinians to achieve peace between them.
Mr. Trump’s appearance beside King Abdullah came amid a flurry of deepening international crises in Syria and North Korea, and just hours after news broke of the president’s decision to remove Stephen K. Bannon, his chief strategist, from a key committee at the National Security Council.
Mr. Trump took questions from reporters after new reports that North Korea had fired a ballistic missile on Tuesday night, increasing concerns about Kim Jong-un, North Korea’s leader, on the eve of a summit between Mr. Trump and Xi Jinping, the president of China.
Secretary of State Rex W. Tillerson issued a short statement after the test, saying bluntly: “The United States has spoken enough about North Korea. We have no further comment.”
The decision to remove Mr. Bannon from the principals committee at the National Security Council reverses one of the president’s most contentious early national security actions. His original National Security Council included Mr. Bannon on the key committee, but demoted the role of several intelligence officials.
In the meetings with King Abdullah, Mr. Trump planned to talk about his hopes for negotiating a peace agreement between Israel and the Palestinians with the help of Arab neighbors. While such an accord has eluded other presidents, Mr. Trump has expressed confidence that he and his son-in-law, Jared Kushner, can bring the warring parties together.
Jordan could be important to any negotiation. Home to many Palestinian refugees, it is one of just two Arab states with a peace treaty with Israel and acts as custodian of Muslim holy sites in Jerusalem. King Abdullah has long been viewed as one of the most moderate of Arab leaders and close to a string of American presidents. He recently hosted Jason Greenblatt, Mr. Trump’s envoy, in Jordan.
King Abdullah’s visit made him the first foreign leader to talk with Mr. Trump twice in person since the president took office. Fearing a violent backlash if Mr. Trump followed through with promises to move the American embassy in Israel to Jerusalem, the king flew uninvited to Washington in January to buttonhole the president at a prayer breakfast and implore him to hold off. Mr. Trump obliged and has indicated he is rethinking such a move.
But Mr. Trump has abandoned American insistence on the creation of a Palestinian state as the basis for any peace deal, a key condition for Jordan and other Arab states. Mr. Trump has said he could accept such a two-state solution but would also be fine with a one-state solution, if that was agreed to by the two sides.
For King Abdullah, the visit was also important as the civil war in Syria escalates. Jordan has absorbed more than 600,000 Syrian refugees and become especially dependent on American and western assistance to cope with the influx.