Speaking out against Muammar al-Qaddafi for the first time, President Obama said on Saturday the Libyan leader needs to "leave now," having lost the legitimacy to rule.

In a White House statement on Obama's telephone call with German Chancellor Angela Merkel, Obama took his most direct position yet on the escalating violence in Libya.

"The president stated that when a leader's only means of staying in power is to use mass violence against his own people, he has lost the legitimacy to rule and needs to do what is right for his country by leaving now," it said.

Obama's stance comes after he signed an executive order Friday freezing assets held by Qaddafi and four of his children in the United States. The Treasury Department said the sanctions against Qaddafi, three of his sons and a daughter also apply to the Libyan government.

Secretary of State Hillary Rodham Clinton announced further sanctions Saturday, revoking visas for senior Libyan officials and their immediate family members. She said future applications from those blacklisted for travel to the United States would be rejected.

Qaddafi "should go without further bloodshed and violence," Clinton said in a separate statement.

Obama has been conferring with world leaders about the unrest in Libya. The administration is hoping that the world speaks with a single voice against Qaddafi's violent crackdown on protesters, and Obama is sending Clinton to Geneva on Sunday to coordinate with foreign policy chiefs from several countries.

The U.N. Security Council met urgently Saturday and voted unanimously to impose new sanctions against Libya.

Secretary-General Ban Ki-moon wants immediate action to protect Libyan civilians. The U.N. chief was due in Washington on Monday for talks with Obama at the White House.

The administration had been facing increasing pressure to more forcefully condemn Qaddafi and explicitly call for his ouster, as French President Nicolas Sarkozy has done. Witnesses in Libya said Qaddafi is arming civilian supporters to set up checkpoints and roving patrols in Tripoli, the capital.

The U.S. held back, but its tone shifted sharply on Friday after Americans in Libya were evacuated to safety by ferry and a chartered airplane.

Shortly after, Obama signed an executive order outlining financial penalties designed to pressure Qaddafi's government into halting the violence. The order said that the instability in Libya constituted an "unusual and extraordinary threat" to U.S. national security and foreign policy.

A nonviolent revolt against Qaddafi's government began Feb. 15 amid a wave of uprisings in the Arab world. Most of Libya's eastern half is under the control of rebels. Witnesses say Qaddafi's government has responded by shooting at protesters in numerous cities.

The Associated Press contributed to this report.