U.S. President Barack Obama on Thursday urged Syrian President Bashar Assad to resign "for the sake of the Syrian people."
"The time has come for President Assad to step aside," he said in a written statement.
"His calls for dialogue and reform have rung hollow while he is imprisoning, torturing, and slaughtering his own people," the U.S president went on.
Obama also announced "unprecedented sanctions to deepen the financial isolation of the Assad regime and further disrupt its ability to finance a campaign of violence against the Syrian people".
His remarks come in stark contrast to Secretary of State Hillary Clinton's comments on Tuesday to the effect that the United States would not call for Assad's removal.
Syria has been rocked by mass protests demanding reforms and the resignation of Assad for almost six months. Pressure from international powers has mounted to end the crackdown.
About 2,000 civilians are thought to have been killed since protests began in the southern city of Deraa in mid-March. According to government data, over 500 servicemen and security officers were also killed.
