Have We Learned Nothing from Saddam Hussein and Iraq?
"Today's chemical attack in Syria against innocent people, including women and children, is reprehensible," Spicer said in a prepared statement.
The administration, Spicer said, was "confident" that Assad was to blame but refused to speculate on how the US would respond.
Earlier this week Spicer indicated that the White House no longer saw Assad's departure as necessary for peace.
But amid diplomatic pressure from European allies in Britain and France, the White House signaled a tougher line.
"The idea that someone would use chemical weapons on their own people, including women and children, is not something that any civilized nation should sit back and accept or tolerate," he said.
"I think it's in the best interest of the Syrian people to not have anybody who would do the kind of heinous acts," said Spicer.