Yet the initial bafflement among U.S. defense officials after the warning came late Monday, coupled with the simultaneous distraction of President Trump's unrelated tweets, by Tuesday seemed to undercut the seriousness of the charge. More broadly, the episode is a test of the damage Trump has done to his and his administration's trustworthiness by his assaults on the U.S. intelligence community and other perceived enemies.
Trump has spent months attacking the credibility of the intelligence community, at one point comparing operatives' tactics to Nazis' and repeatedly dismissing findings of Russian meddling in the election as a "hoax" and "witch hunt" — even as foreign policy experts cautioned that he was diminishing the reputation of a community he would need in times of crisis to rally public support.
His military threat to Syria, which is closely allied with Russia, comes as Trump is also moving to send more troops to fight in Iraq and perhaps Afghanistan, and a separate crisis builds with nuclear-armed North Korea. That suggests Trump will need to lean more and more on the work and reputation of intelligence officials to make a case for his administration's actions overseas.
"At a moment of crisis when U.S. decisions and actions rest upon information coming from the intelligence community, [Trump] may have diminished the credibility of that information in the eyes of the public and the eyes of the international community," said Daryl Kimball, executive director of the Arms Control Assn.
Kimball called the preemptive White House statement on Syria "unusual." He said such messages would normally be sent through private diplomatic channels and, once public, should be followed by a formal presentation of evidence to the U.N. Security Council to build international support for action against suspected Syrian violations of the chemical weapons ban.
What was also unusual was that such an ominous warning — with its threat of deeper U.S. engagement in Syria's civil war — received relatively little attention on Capitol Hill or in the media on Tuesday compared with similar alarms from past administrations.
The four-line statement on Syria from the White House press secretary came just after 9:44 p.m. Monday.
"The United States has identified potential preparations for another chemical weapons attack by the
If Syrian President Bashar Assad "conducts another mass murder attack using chemical weapons, he and his military will pay a heavy price," it concluded.
The United States struck Syria with 59 missiles after the April chemical attack, but the administration's new warning suggests that strike may not have deterred the Assad government.
A Pentagon spokesman confirmed Tuesday that preparations for a chemical attack were observed at the same base in Syria from which its military launched a sarin nerve gas attack that killed more than 70 people, including children, in April.
"We have observed activities at Shayrat Air Base that suggest possible intent by the Syrian regime to use chemical weapons again," Pentagon spokesman Maj. Adrian J.T. Rankine-Galloway said in a statement. "These activities are similar to what we observed prior to the regime chemical weapons attack against Khan Sheikhoun in April."
But some senior U.S. defense and intelligence officials reached late Monday and early Tuesday were caught off guard by the White House statement. "Some knew, some didn't," said a U.S. official who sought anonymity to discuss the intelligence matter.
The official described the release of the nighttime statement as "ungraceful," but said the assessment that Syria was preparing for an attack is sound.
Such official statements are typically distributed widely across an administration for internal vetting before they're publicly released. The White House said the relevant agencies were informed before the statement was published.
Top officials at the State Department, Defense Department, Office of the Director of National Intelligence and CIA were "fully aware" of the statement, White House Deputy Press Secretary Sarah Huckabee Sanders told reporters Tuesday.
By going public, the White House hoped to prevent Assad from launching another sarin gas attack, Sanders said.
"Our goal every day to do what we can to protect life in all forms and to take steps to move the ball forward in defeating ISIS and defeating all efforts of terrorism. I think the statement yesterday helped to do that," Sanders said.
Asked why a statement should be expected to deter Assad from using chemical weapons when airstrikes in April didn't seem to, she replied, "I don't know that it didn't based on what we know at this point."
Trump raised questions about the urgency of the matter, and his own level of concern, by sending out a tweet about domestic politics only minutes later. He cited a Fox News report about the FBI's Russia investigation, writing as he often does about the inquiry: "Witch Hunt!"
Trump continued with similar tweets through the next morning, assailing "fake news" but writing nothing about Syria.
The Syria statement prompted a sharp backlash from the Kremlin, which is Assad's military ally. Russian officials denied there is evidence of an imminent chemical attack and called the White House threat "unacceptable."
The tension between the United States and Russia has heightened as Trump has been expected to meet Russian President Vladimir Putin next week at the Group of 20 summit of industrialized nations in Germany. Monday's statement may be seen as a warning not just to Syria but to Russia, which is widely seen as enabling Assad's harsh tactics by bolstering his military as he has tried to retain power.
The statement "was a good idea to deter a possible chemical weapons attack if the intelligence was there," Michael Allen, a former senior director on the National Security Council in the George W. Bush White House, said in an interview. Warning Syria, he added, might strengthen U.S. leverage with Moscow "if the Russians conclude perhaps we have a president willing to use force when appropriate."