Russia knew in advance of Syria's plan to unleash chemical weapons on civilians, the Associated Press reported Monday, sourcing the report to a "senior U.S. official" who spoke on condition of anonymity.
"The official says a Russian-operated drone flew over a hospital in Syria as victims of the attack were rushing to get treatment," the AP reported. "Hours after the drone left, a Russian-made fighter jet bombed the hospital in what American officials believe was an attempt to cover up the usage of chemical weapons."
It hadn't previously been clear whether the drone was Syrian or Russian. It still isn't clear whose jet bombed the hospital.
Ahead of Secretary of State Rex Tillerson's planned visit to Moscow, officials of President Donald Trump's administration have pushed Russia to break its alliance with the Assad regime, saying continued support for the Syrian president will imperil U.S-Russian relations.
The AP report came after Sen. John McCain said at a news conference in Belgrade that he believed Russia had colluded with the Syrian government in last Tuesday's attack on Khan Sheikhoun, which killed more than 80 people, including children.
The chemical strike spurred the United States to deploy 59 Tomahawk missiles at the Ash Sha'irat airfield, from which the chemical attack originated.
Defense Secretary Jim Mattis said in a statement Monday that the missile assault resulted in "the damage or destruction" of 20% of Syria's operational aircraft. Mattis said the air field, which the Syrian government has since used, is essentially non-functional from a military standpoint because it can no longer handle the refueling or re-arming planes.
"The Syrian government would be ill-advised ever again to use chemical weapons," Mattis warned.
The White House did not immediately respond to the report, but advance Russian knowledge of the use of chemical weapons would no doubt heighten tensions as the U.S. seeks to both fight the Islamic State terror network in Syria and push for the end of Assad's control.
Earlier Monday, White House press secretary Sean Spicer said the U.S. had not ruled out the possibility of further military action against the Syrian government.
An ABC News/Washington Post poll released Monday found Americans divided on Trump's missile strike on Syria, noting 59% of Americans "are concerned about Friday's missile strike worsening U.S. relations with Russia."