JERUSALEM — Prime Minister Ariel Sharon fought for his life today following seven hours of emergency surgery to stop widespread bleeding in his brain. The massive stroke made it unlikely that he would return to power.

Vice Premier Ehud Olmert was named acting prime minister and convened the Cabinet for a special session, where Sharon's large chair at the center of the long oval table remained empty. "This is a difficult situation that we are not accustomed to," Olmert told the somber ministers.

A brain scan after surgery showed that the bleeding had been stopped, and the 77-year-old prime minister was transferred to the intensive care unit, said Dr. Shlomo Mor-Yosef, the director of Hadassah Hospital in Jerusalem.

At a midafternoon briefing, Mor-Yosef said Sharon was in serious but stable condition on a respirator in "deep sedation." He will remain sedated for another 24 hours at least, Mor-Yosef said.

Sharon's sudden turn for the worse, at the height of his popularity, stunned Israelis, who had relied on the tough ex-general to steer them through turbulent times. Rabbis called Israelis to flock to synagogues and say special prayers.

The daily newspaper Yediot Ahronot ran a headline that said: "The last battle."

Palestinians followed reports on Sharon's condition with a mix of apprehension and glee, and some officials said they feared the dramatic events would derail Jan. 25 parliament elections in the West Bank and Gaza. Despite his pullout from Gaza last year, Sharon is still widely reviled in the Arab world for his tough actions against Palestinians.

Palestinian leader Mahmoud Abbas contacted Israeli officials to express concern over Sharon's health, an Abbas aide said.

Close Sharon associates said they did not expect him to return to office.

Despite his illness, Israel's elections will be held as scheduled on March 28, Attorney General Meni Mazuz said after the Cabinet meeting. Sharon had been expected to easily win re-election at the head of the moderate Kadima Party he created to free his hands for further peace moves with the Palestinians.

Many Israelis see Sharon — an overweight war hero and longtime hawk who changed tack and withdrew from the Gaza Strip last year — as the best hope for achieving a peace deal with the Palestinians. His illness would create a power vacuum in the government and cloud Kadima's prospects.

Sharon was put in an ambulance at his ranch Wednesday evening after complaining of feeling unwell. The stroke happened during the hourlong drive to Hadassah, Dr. Shmuel Shapira told Channel 10 TV.

At Hadassah, doctors put him on a respirator and began emergency surgery about midnight. Doctors said they had stopped the bleeding during initial surgery, but Sharon was sent back to the operating room because a brain scan showed he required more treatment. He later had a second scan before being moved to the ICU, Mor-Yosef said.

Surgery apparently had been complicated by blood thinners Sharon took following a mild stroke Dec. 18. The medication may also have contributed to Wednesday's stroke. Sharon originally had been scheduled to undergo a procedure today to seal a hole in his heart that contributed to the initial stroke.

Mor-Yosef did not give a prognosis, but neurosurgeons not involved in Sharon's treatment said a full recovery was not likely following such a massive stroke. They said it usually takes at least a day after surgery to determine the extent of any damage.

Outside doctors said chances of recovery were slim, especially because of the length of the surgery.

"For them to have to go back in twice, that's not good," said Dr. Emil Popovic, a neurosurgeon at Sir Charles Gairdner Hospital in Perth, Australia. "At 77, not too many people make a good recovery from a brain hemorrhage."

U.S. National Security Council official Elliott Abrams and State Department official David Welch were to have met with Sharon tonight, apparently to urge Israel to reverse a decision to ban Palestinian voting in disputed Jerusalem. But Palestinians said that they had postponed their trip to the region because of Sharon's illness. Japanese Prime Minister Junichiro Koizumi also postponed his visit, scheduled for Sunday.

Abbas has said he may not hold elections if Jerusalem, claimed by the Palestinians as a capital, is excluded.

"We hope that this (Sharon's illness) will not affect what we had expected of the Israelis," said Palestinian negotiator Saeb Erekat. If Olmert puts off a decision on Jerusalem, "it means the Palestinian election is going down," Erekat said.

Israelis and world leaders expressed concern and offered prayers for Sharon.

President Bush praised Sharon as "a man of courage and peace," saying he and first lady Laura Bush "share the concerns of the Israeli people ... and we are praying for his recovery."

Arab TV broadcasters beamed out largely straightforward, nonstop live coverage about Sharon.

Ahmed Jibril, a radical Palestinian leader in Damascus, Syria, called the stroke a gift from God.

Sharon aide Raanan Gissin warned Israel's enemies: "To anyone who entertains any notion to try and exploit this situation ... the security forces and IDF (Israeli military) are ready for any kind of challenge," he said.

But a Palestinian commentator on the Saudi-owned Al-Arabiya network offered Sharon unexpected praise as "the first Israeli leader who stopped claiming Israel had a right to all of the Palestinians' land," a reference to Israel's Gaza withdrawal.

"A live Sharon is better for the Palestinians now, despite all the crimes he has committed against us," said Ghazi al-Saadi.