Israelis and world leaders have already braced themselves for the end of the Sharon era, fearing his demise will spark new turmoil in a region struggling to find the path to peace after decades of conflict.
Even if he were to pull through, few people believe the 77-year-old will be in any condition to return to the helm and lead his new Kadima party in a March general election.
In a bulletin issued to reporters nearly three days after Sharon was admitted to hospital, medics said the latest brain scan had shown signs of improvement and that all his other "vital signs were within normal limits".
However, Professor Shlomo Mor Yosef, director of the Hadassah hospital, said that the prime minister remained "still critical and stable".
Doctors would only be able to assess the full extent of the damage caused to Sharon's brain after they had woken him from a medically induced coma. A decision on when to try to awaken him would be made on Sunday morning.
Asked by reporters about his assessment of the damage, he said: "That is the question we all want answered ... Until we wake the prime minister up we won't be able to answer that question."
The surgeon leading the battle to save Ariel Sharon's life had earlier said he was more "optimistic" after the results of the morning's scan.
"The scan is better than yesterday's. I am more optimistic," Argentinian neurologist Felix Umansky said. "Ariel Sharon is in a stable condition and given his situation, this is good news," he added.
Sharon has been treated at Jerusalem's Hadassah hospital since Wednesday after suffering a massive stroke and has undergone three bouts of surgery to stem bleeding in his brain.
As Israelis, no strangers to times of crisis, prayed for Sharon on the Jewish Sabbath, US Secretary of State Condoleezza Rice cleared her diary by cancelling a trip to Indonesia and Australia.
Just days ago, Sharon, who has been premier since early 2001, and his new centrist Kadima party had seemed a shoo-in for a general election set for March 28 but all previous calculations are now being revised.
British foreign secretary Jack Straw warned that Israel faced a period of great uncertainty while Sharon fought for his life.
"Of course Ariel Sharon was perhaps the most dominant single figure in the whole of Middle East politics and therefore he leaves a hole for everybody. "There's a great uncertainty in the short term," Straw said. But "even if Ariel Sharon had been well" there would have been little movement on the political level "until the end of March and the formation of a new government".
Before Israel goes to the polls, the Palestinians are also scheduled to elect their own new government on January 25.
Although Palestinian leader Mahmoud Abbas has said Sharon's plight should have no impact on the ballot, he has also threatened to postpone it if Israel does not guarantee that voting can take place in occupied east Jerusalem.
The decision will now lie in the hands of deputy premier and finance minister Ehud Olmert, who is replacing Sharon while he lies stricken.
Marwan Barghouti, leader of the five-year Palestinian uprising, warned Abbas against any move to use Sharon's health crisis as a pretext to shelve the vote.
"The election is a national Palestinian issue and it must not be linked to any foreign concerns such as what is happening in Israel with Sharon," said Barghouti, serving five life sentences in an Israeli jail, in a message printed in Palestinian newspapers.
© 2005 Agence France-Presse
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