The life-and-death struggle of Minister Ariel Sharon continued into a second day Thursday after the Israeli prime minister suffered a massive stroke.

Sharon remained in stable but severe condition at Hadassah Hospital in Jerusalem after doctors performed a seven-hour surgery to stop the bleeding in his brain. At a mid-afternoon press conference (around 7 a.m. ET), Hadassah Hospital Director Shlomo Mor-Yosef said Sharon was under anesthesia on a respirator in "deep sedation" and would be on a ventilator for at least the next 24 hours.

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, Mor-Yosef said.

He denied widespread rumors that Sharon's condition was far worse than doctors have let on and promised to issue immediate updates on any change.

Sharon's sons, Omri and Gilad, were at their father's bedside. Rabbi David Grossman, a family friend, said of them: "You don't see tears. You see hope, quiet and fortitude."

It's considered unlikely Sharon will return to political power after the latest medical emergency.

Vice Premier Ehud Olmert was named Israel's 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.

Sharon's stroke threw Israeli politics and diplomacy throughout the region into turmoil amid election campaigns for both Israel and the Palestinians.

Despite Sharon's illness, Attorney General Meni Mazuz said following the Cabinet meeting that Israel's elections will be held as scheduled March 28.

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.

"It's unclear now who is going to lead that party ... now it appears to be unstable," Amb. Alon Pinkas, former Israeli consul general, told FOX News on Thursday, noting that the party is an interesting collection of right- and left-wing politicians, as well as centrists.

"The whole thing is a one man-show ... will there be someone to succeed him?" Pinkas asked. "There are good people in that party who are well experienced and capable to do that but that party doesn't even have a mechanism which they can select or appoint that person, which is why it's chaotic right now."

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 the electoral prospects of his party, which was built around Sharon.

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 Thursday to express concern over Sharon's deteriorating health, an Abbas aide said.

Sharon fell ill at his ranch Wednesday evening and was rushed to Hadassah Hospital, where doctors put him on a respirator and began emergency surgery about midnight (5 p.m. EST Wednesday).

Doctors said Thursday morning 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 underwent a second scan before being sent 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 Thursday to seal a hole in his heart that contributed to the initial stroke.

Mor-Yosef did not address Sharon's 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."

Palestinian officials said they were concerned the uncertainty in Israel could overshadow their campaign for Jan. 25 elections.

U.S. National Security Council official Elliott Abrams and State Department official David Welch were to have met with Sharon on Thursday evening, 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.

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.

Japanese Prime Minister Junichiro Koizumi also postponed his visit, scheduled to begin Sunday.

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."

Secretary of State Condoleezza Rice said, "Our thoughts and prayers are with Prime Minister Sharon, his family and the Israeli people."

"We wish the prime minister a full recovery," she said in a statement.

A spokesman for Kofi Annan said the U.N. secretary general is "deeply concerned about the health" of Sharon. "He is following developments closely and very much hopes that the prime minister will make a speedy recovery. His thoughts are with Mr. Sharon and his family, as well as with the government and people of Israel," the spokesman said.

Israel's stock market plunged 5.4 percent on news of Sharon's stroke.

Israeli Chief Rabbi Yona Metzger called on Israelis to read Psalms and pray for Sharon.

"We are very, very worried," he said, and prayed for "mercy from Heaven."

Pan-Arab satellite television broadcasters beamed out largely straightforward, nonstop live coverage from outside the hospital where Sharon — a particularly despised figure among many Arabs — struggled for his life.

Ahmed Jibril, leader of the Popular Front for the Liberation of Palestine, General Command, a radical leftist Palestinian group based in Damascus, Syria, called the stroke a gift from God.

Speaking to reporters outside the hospital, 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."

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.

According to Israeli law, Olmert, as vice premier, assumed the post of acting prime minister for 100 days. An election will be held in that time, apparently on March 28. If Sharon should die, the Cabinet would choose a replacement, said legal analyst Moshe Negbi.

Sharon has been prominent in Israeli life for more than five decades. He first rose to prominence as an army officer in the 1950s, advancing through the ranks and gaining attention during the 1967 war. He left the military for politics, forging the hard-line Likud Party, which came to power in 1977.

As defense minister, Sharon directed Israel's ill-fated invasion of Lebanon in 1982 during which an Israeli commission found him indirectly responsible for a massacre of Palestinians in the Sabra and Chatilla refugee camps by Christian Phalangist militiamen.

Sharon re-emerged as prime minister in 2001 soon after the outbreak of a new round of Israeli-Palestinian violence, and two years later he reversed his decades-long course of supporting Jewish settlements in the West Bank and Gaza, and pushed through a plan to withdraw from Gaza and part of the West Bank. The pullout was completed in September.

The withdrawal fractured Likud, and he bolted to form Kadima. He was putting together a list of candidates for the election when he fell ill Wednesday.

In the election, Sharon was to face off against Likud's candidate, former Prime Minister Benjamin Netanyahu, and Amir Peretz, a union leader who recently took control of the dovish Labor Party.

Olmert, who could emerge as Sharon's successor as head of Kadima, would likely have a far tougher time in the election than Sharon, Israel's most popular politician.

Sharon was put in an ambulance at his ranch in the Negev Desert after complaining of feeling unwell. The stroke happened during the hour-long drive to Hadassah Hospital, Dr. Shmuel Shapira of the hospital told Channel 10 TV.

After his stroke last month, doctors said he would not suffer long-term effects, but they discovered a birth defect in his heart that apparently contributed to the stroke. They originally planned to fix the hole in a procedure Thursday.

He took blood thinners after the first stroke to prevent another clot, but such drugs also raise the risk of cerebral hemorrhages.

The Associated Press contributed to this report.