MILAN (REUTERS) - Silvio Berlusconi is expected to undergo surgery on Tuesday (June 14), his doctor said on Saturday, after the four-time Italian prime minister was admitted to hospital this week with a heart problem.

A spokeswoman for Milan's San Raffaele hospital, where the 79-year-old centre-right leader will have a defective aortic valve replaced, confirmed the comment made to reporters by Berlusconi's personal doctor Alberto Zangrillo.

The media mogul said in a message on Facebook on Friday his Forza Italia party was perfectly able to function despite his absence, ahead of a run-off vote in municipal elections on June 19.

Berlusconi was admitted to hospital on Monday suffering from what his doctors called a cardiac deficiency.

"He risked dying. He was in a really serious, worrying condition and he knew it," Berlusconi's personal doctor Alberto Zangrillo told reporters on Thursday.

"For a man who wants to live to be 130, this is a very unpleasant jolt."

After the news of the diagnosis sank in, he "showed great courage and determination" and "put his complete trust in us", Zangrillo said, adding that he should have fully recovered from the surgery within a month.

He said there was a 2 per cent risk of mortality tied to the operation, which was expected to last four hours.

Earlier on Thursday, a spokeswoman for his Forza Italia (Go Italy!) party had denied press reports that Berlusconi, who has worn a pacemaker since he was 70, would need an operation.

Berlusconi's once powerful centre-right has become increasingly fragmented in recent years, especially since he lost his grip on power in 2011 at the height of the euro zone debt crisis.

His party suffered mixed fortunes in Sunday's local elections, with his candidate to become mayor in Rome coming a lowly fourth. The bruising campaign took its toll on

Berlusconi and his doctor said he would benefit from quitting politics.

There is no indication that Berlusconi is ready to follow his advice.