Washington ? Ratcheting up the pressure, President Barack Obama on Saturday said Moammar Gadhafi has lost his legitimacy to rule and urged the Libyan leader to leave power immediately.

It was the first time Obama has called for Gadhafi to step down, coming after days of bloodshed in Libya. Gadhafi has vowed to fight to the end to keep his four-decade grip on power in the North African country.

“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,” the White House said in a statement, summarizing Obama’s telephone conversation with German Chancellor Angela Merkel.

Until now, U.S. officials have held back from such a pronouncement, insisting it is for the Libyan people to decide who their leader should be.

Secretary of State Hillary Rodham Clinton said Libyans “have made themselves clear.”

“Gadhafi has lost the confidence of his people and he should go without further bloodshed and violence,” she said in a separate statement. “The Libyan people deserve a government that is responsive to their aspirations and that protects their universally recognized human rights.”

The administration upped its pressure a day after it froze all Libyan assets in the U.S. that belong to Gadhafi, his government and four of his children. The U.S. also closed its embassy in Libya and suspended the limited defense trade between the countries.

Clinton announced further sanctions Saturday, revoking visas for senior Libyan officials and their immediate family members. She said applications from these people for travel to the United States would be rejected.

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 Gadhafi’s violent crackdown on protesters, and Obama is sending Clinton to Geneva on Sunday to coordinate with foreign policy chiefs from several countries.

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

Also on Saturday, the U.N. Security Council voted unanimously to impose sanctions on Libyan leader Moammar Gadhafi, his five adult children and top associates.

Voting after a day of discussions — interrupted at times for consultations with home capitals — council members agreed to freeze the assets of Gadhafi, his four sons and one daughter, and to ban travel by the whole family plus 10 close associates.

All 15 nations on the council ultimately approved referring the case to the permanent war crimes tribunal.