WASHINGTON — President Trump has drawn a new red line for President Bashar Assad of Syria, with US officials describing preparations at a Syrian air base for a chemical weapons assault as they sought Tuesday to bolster Trump’s threat to deter an attack.
But the administration elaborated little on the president’s unexpected, 87-word statement a night earlier that warned that Assad would “pay a heavy price’’ if he again releases toxic gas on rebel-held territory, leaving lingering questions in Washington and in the Middle East about Trump’s intentions in Syria.
US officials have declined to rate their level of confidence about whether a chemical attack is imminent or say whether the administration has pursued diplomatic channels to stop it. Military officials, who were initially caught off-guard by Monday night’s White House statement, would not discuss what options they are considering. Conversations with allies about the chemical weapons intelligence have been kept largely secret.
In previous administrations, debates about how best to deter atrocities have played out publicly around the world. President George W. Bush took months to argue his case — later proved to be flawed — about the existence of weapons of mass destruction in Iraq. President Obama offered detailed explanations about his deliberations on how to respond when Assad used chemical weapons to kill 1,400 people in 2013.
On Tuesday, White House officials said only that Trump’s statement spoke for itself.
That silence added to the uncertainty about whether a new military confrontation with Syria is looming just two months after US forces fired dozens of Tomahawk missiles at the Syrian base, Al Shayrat airfield, after a chemical weapons attack that killed dozens.
Assad’s government vigorously denied the accusation of preparations for an attack, calling Trump’s statement a provocation. And in Russia, a close ally of Syria’s, a senior lawmaker accused the United States of using the declaration about chemical weapons to plan an attack on Syria.
As if to punctuate his contempt for the Trump administration’s warning, Assad visited a Russian air base near Latakia in the western part of the country on Tuesday, accompanied by General Valery V. Gerasimov, the Russian military’s chief of staff. Syrian news media, which reported the visit, distributed a video clip of Assad climbing into the cockpit of a Russian Sukhoi Su-35 parked at the base, where Russia has conducted many of its bombing operations to support the government’s side in the six-year civil war.
In Washington on Tuesday, US officials explained only briefly what prompted the White House effort at deterrence. Captain Jeff Davis, a Pentagon spokesman, told reporters that what looked like active preparations for a chemical attack had been seen at Al Shayrat. One Pentagon official said an aircraft shelter at the base that had been hit by a US Tomahawk missile in April was being used for the preparation.
Monday’s statement caught military officials by surprise, with one at the US Central Command, which oversees combat operations in the Middle East, saying at the time that he had “no idea’’ what the White House statement was referring to.
A White House spokeswoman, Sarah Huckabee Sanders, said Tuesday that relevant agencies, including the Pentagon, the State Department, the CIA, and the Office of the Director of National Intelligence, were involved in issuing the statement. But White House officials repeatedly declined to provide details about the timing or content of the deliberations.
A US defense official said that Defense Secretary Jim Mattis was aware of the movements at Al Shayrat and that the White House statement was coming.
