World leaders on Thursday responded with concerns about the destinies of both Israeli Prime Minister Ariel Sharon and the Middle East peace process after the 77-year-old hawkish leader was put on a respirator for at least 48 hours.

Spokesman for Kofi Annan said the UN chief "is following the developments closely and very much hopes that the prime minister will make a speedy recovery."

Annan had been in touch with Israel's ambassador to the United Nations and had discussed Sharon's health and the situation in the Middle East with US Secretary of State Condoleezza Rice, the spokesman said.

U.S. President George W. Bush said "our nation sends our deepest sympathies to Ariel Sharon."

"He lies immobilized in an Israeli hospital. We pray for his recovery. He's a good man, a strong man, a man who cared deeply about the security of the Israeli people and a man who had a vision for peace. May God bless him," Bush said.

The French presidential office said President Jacques Chirac hoped Sharon "will overcome the painful trial he is going through."

Chirac said he wanted to see continued "courageous initiatives started by Mr. Sharon that have already won approval from the entire international community."

Italian Premier Silvio Berlusconi said on a morning radio talk show that "those who understand the situation in Israel know that Sharon's decision to close the (Jewish) settlements and withdraw Israeli troops from Gaza was a courageous decision which was opposed by many in his own party."

In a message of support to Sharon, South African President Thabo Mbeki said: "It is our wish and hope that you will recover to resume your responsibility in leading the government and peopleof Israel."

In Australia, Foreign Minister Alexander Downer praised Sharon for "a pivotal role in the Middle East peace process."

"Australia hopes that all parties to the Middle East peace process continue the work of Mr. Sharon to bring the roadmap for the Middle East peace process to fruition," Downer said.

Palestinian leaders also expressed concerns and wished Sharon a speedy recovery.

Palestinian President Mahmound Abbas voiced his concerns about Sharon's health in a phone call to senior Israeli officials, Abbas' aide Nabil Abu Rudeineh said on Thursday.

Palestinian Prime Minister Ahmed Qurei wished Sharon a speedy recovery. "What concerns us is having a true and serious peace process and we look toward an Israeli leadership that supports peace and will be able to negotiate with the Palestinians," he said.

In Israel, acting Prime Minister Ehud Olmert said the general elections would be held as scheduled on March 28 despite that Sharon remained in critical condition.

But Olmert was being challenged by ministers from Israel's rightist Likud party, who vowed not to resign from the government as planned in light of Sharon's failing health.

Health Minister Dan Naveh told Israel's Channel 1 television that the walkout, scheduled for Sunday ahead of the March 28 general elections, "will not happen."

Challenges also came from Palestinian militant groups. The Islamic Resistance Movement (Hamas) said the Middle East would be a better place without Sharon.

Hamas spokesman Musheer al-Masri urged the Palestinian leadership not to be influenced by changes in Israel's politics.

Anwar Abu Taha, a senior leader of the Islamic Jihad termed Sharon as "one of the tyrants who has committed scores of bloody massacres against the Palestinian people."

In the West Bank town of Nablus, Palestinian gunmen fired into the air to show glee over Sharon's illness, witnesses said.

Sharon was transferred to hospital Wednesday night after suffering from chest pains. He was later diagnosed with a major stroke and a massive internal bleeding in the brain, and has since remained under heavy sedation.