WASHINGTON — The White House said late Monday that President Bashar al-Assad of Syria appeared to be preparing another chemical weapons attack, and warned that he would “pay a heavy price” if one took place.
In a statement from his press secretary, President Trump said that Mr. Assad’s preparations appeared similar to the ones that Western intelligence officials believe were made by the Syrian government before chemical attacks in April that killed dozens of Syrians, including children.
“As we have previously stated, the United States is in Syria to eliminate the Islamic State of Iraq and Syria,” the White House statement said. “If, however, Mr. Assad conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price.”
Several military officials who were reached late Monday said they had been caught off guard by the White House statement, but it was unclear how closely held the intelligence regarding a potential chemical attack was.
Brian Hale, a spokesman for the director of national intelligence, referred questions to the White House. Marc Raimondi, a spokesman for the White House’s National Security Council, said, “We are letting the statement speak for itself.”
But Nikki R. Haley, the American ambassador to the United Nations, made clear that the United States was taking the latest threat seriously. “Any further attacks done to the people of Syria will be blamed on Assad, but also on Russia & Iran who support him killing his own people,” Ms. Haley tweeted late Monday.
The message appeared designed to set the stage for another possible military strike by Mr. Trump. After Mr. Assad allegedly used chemical weapons in the spring, the American military fired 59 Tomahawk cruise missiles at the air base his government had used to launch the attack.
After Mr. Trump struck the air base, American officials said he had been deeply shaken by graphic photos of Syrian children gasping for breath and dying as a result of the chemical weapons they accused Mr. Assad of using.
“What happened in Syria is truly one of the egregious crimes, and it shouldn’t have happened,” Mr. Trump told reporters then. “And it shouldn’t be allowed to happen.”
It was unclear Monday evening what evidence the American government had of preparations for another, similar attack. But the statement from the White House said it appeared that a new chemical weapons attack “would likely result in the mass murder of civilians, including innocent children.”