Israeli PM Ariel Sharon, after a massive stroke on Jan 4 underwent a surgery since the scan showed fresh bleeding in his brain.
The PM is in a critical situation and is 77 years old.
He is in intensive care at the Hadassah Hospital in Jerusalem where he has already had seven hours of surgery to try and stop bleeding in his brain.
As a statement by Dr Shmuel Shapira, deputy director of Hadassah Hospital, "The goal of the sedation is to lower the oxygen needs of the brain and to allow the brain ... to rest. So certainly until Sunday, and it's possible beyond that, he will be sedated."
But fresh bleeding was observed later. "It was decided to take the prime minister to the operating room to deal with these issues - to stop the bleeding and reduce cranial pressure," doctors said.
Jack Straw, the Foreign Secretary, today joined the international tributes to Mr Sharon, and said he was hoping and praying "for a miracle".
"This man is a man not only of great political courage but of astonishing physical courage and resilience as well," said Jack Straw, the Foreign Secretary. "He's already had a huge effect on the region."
Jewish community leaders and Palestinian campaigners have expressed fears for the future.
"No one knows what effect Sharon dying could have on the peace process, on his newly-formed party Kadima, and the forthcoming elections," said Ephraim Borowski, a director of the Council of Jewish Communities.