US defence secretary James Mattis said on Wednesday that the Syrian government of president Bashar al-Assad appeared so far to have heeded a warning this week from Washington not to carry out a chemical weapons attack.
But Russia, the Syrian government's main backer, said the US assertions that Mr Assad's forces may have been planning a chemical attack complicated peace talks on ending Syria's six-year-old civil war.
The White House said on Monday it appeared the Syrian military was preparing to conduct a chemical weapons attack and Mr Assad and his forces would "pay a heavy price" if it did so.
US officials later said the warning was based on intelligence that indicated preparations for such a strike were under way at Syria’s Shayrat airfield.
"It appears that they took the warning seriously," Mr Mattis said. "They didn't do it," he told reporters flying with him to Brussels for a meeting of Nato defence ministers. He offered no evidence other than the fact that an attack had not taken place.
Asked whether he believed Mr Assad’s forces had called off any such strike completely, Mr Mattis said: “I think you better ask Assad about that.”
Washington accused Syrian forces of using the Shayrat airfield for a chemical weapons attack in April. Syria denies this. However, Mr Mattis said Syria's chemical weapons threat was larger than any single location. "I think that Assad's chemical programme goes far beyond one airfield," he said.
US and allied intelligence officers had for some time identified several sites where they suspected Mr Assad’s government may have been hiding newly made chemical weapons from inspectors, a US official familiar with the intelligence said.
The US launched a cruise missile strike on Shayrat in April following the deaths of 87 people in what Washington said was a poison gas attack in rebel-held territory.
‘Far from conclusive’
The intelligence that prompted the administration’s warning to Syria this week was “far from conclusive”, said another US official familiar with the intelligence. “It did not come close to saying that a chemical weapons attack was coming,” the official said.
The US conveyed the warning to Russia via the “deconfliction channel” the two countries use to avoid clashes in Syrian air space, but there is no evidence indicating that this deterred a chemical attack, the official said.
The Syrian military and foreign ministry did not comment on the White House warning, although the state-run al-Ikhbariya television station said the allegations were fabricated.
Russia denounced the warning and dismissed White House assertions that a strike was being prepared as “unacceptable”.
Russian deputy foreign minister Gennady Gatilov on Wednesday told the US not to take unilateral actions in Syria.
He said the US assertions complicated peace talks on Syria, according to RIA news agency.
Russian officials have described the war in Syria as the biggest source of tension between Moscow and Washington and say the April cruise missile strike ordered by US president Donald Trump raised the risk of confrontation between them.
In Washington, the US ambassador to the UN, Nikki Haley, credited Mr Trump with saving Syrian lives. "Due to the president's actions, we did not see an incident," Ms Haley told US politicians. "I would like to think that the president saved many innocent men, women and children."
On the Syrian battlefields, Turkish artillery bombarded and destroyed Kurdish YPG militia targets after the group’s fighters opened fire on Turkish-backed forces in northern Syria.
The US supports the YPG in the fight against Islamic State in Syria, while Nato ally Turkey regards them as terrorists indistinguishable from militants from the outlawed PKK (Kurdistan Workers Party), which is carrying out an insurgency in southeast Turkey.
Reuters