Obama and Secretary of State Hillary ClintonHillary Diane Rodham ClintonIntel Dem decries White House 'gag order' after Bannon testimony 'Total free-for-all' as Bannon clashes with Intel members Mellman: On Political Authenticity (Part 2) MORE have been calling on Assad to step aside for months amid his government's deadly crackdown on protesters that the U.N. estimates has left more than 3,500 dead. Obama signed an executive order in August levying sanctions on Syria in hopes of supporting pro-democracy elements.

But the move on Saturday by the Arab League — generally an ardent supporter of Arab nationalism — to shun one of its own stunned the Middle East, and was expected to ramp up pressure for other international organizations to take concrete action toward Syria. The Arab League action also threatened further economic sanctions against Assad unless he puts an end to political violence.

"These significant steps expose the increasing diplomatic isolation of a regime that has systematically violated human rights and repressed peaceful protests," Obama said.

But Obama was careful to not to let his condemnation of Assad be interpreted as applying also to the Syrian people.

"The United States joins with the Arab League in its support for the Syrian people, who continue to demand their universal rights in the face of the regime’s callous violence," he said.