The Pentagon is investigating whether Russia played any role in last week's deadly chemical attack in Syria, but has determined thus far only that the Syrian government orchestrated it, the U.S. defense chief said on April 11.
"I have personally reviewed the intelligence, and there is no doubt the Syrian regime is responsible for the decision to attack and for the attack itself" on the town of Khan Sheikhun on April 4, killing 87 people, Defense Secretary Jim Mattis said.
While some U.S. officials have said they believe Russia played a role, noting it had forces stationed at the same air base where Syrian planes allegedly launched the attack, Mattis said the United States does not have any proof of Russian involvement.
"It was very clear that the Assad regime planned it, orchestrated it, and executed it, and beyond that we can't say right now," he said.
Mattis warned that if Syria uses chemical weapons again, it will "pay a very, very stiff price."
But he insisted that the United States remains focused on its primary mission in Syria: defeating the Islamic State group.
"The campaign stays on track exactly as it was before Assad's violation," he said.