President Barack Obama says the time has come for Syrian President Bashar Assad to resign for the sake of his brutally repressed people.

In a stinging written statement, Obama said Assad has overseen a vicious onslaught of his people as they protest for freedoms. He said the Syrian people will decide their country's future but Assad is standing in their way and must go.

Obama said Assad's calls for reform ring hollow while he is "imprisoning, torturing and slaughtering his own people."

This was Obama's first explicit call for Assad to step down. His administration was also slapping new sanctions on Syria.

Secretary of State Hillary Rodham Clinton was to speak about the government's tougher stance later Thursday.