The Italian bid is up against the Swedish candidacy of Stockholm and Are, with the IOC to elect the winning bid on Monday.
"We have informed the IOC today that Prime Minister Conte will arrive (in Lausanne) on Monday," the source told Reuters.
The two bids are the last remaining after Swiss city Sion, Japan's Sapporo, Austria's Graz and 1988 hosts Calgary in Canada all withdrew last year, scared off by the cost and size of the Games or strong local opposition to the Olympics.
Turkey's Erzurum was eliminated from the bidding process by the IOC.
"The Prime Minister will come to support the bid of Italy," the source said.
Up until a few years ago bidding for the Games was a fierce affair and campaign budgets grew to as much as $100 million as heads of state attended the vote in order to push for their country's candidacy.
But with interest waning in recent years amid ballooning budgets for hosting the Games, fewer cities are left in the race, forcing the IOC to reform the bid process in an effort to turn the Games into an attractive prospect again.
It has also not been an easy process for Milan and Stockholm, with both having to wait until late to receive much-needed government guarantees and support.
The Swedish bid also suffered a major blow when the City of Stockholm said it would not be signing the host city contract with the IOC should it be awarded the Games, amid strong local opposition. Are would do it instead.
(Reporting by Karolos Grohmann; Editing by Christian Radnedge)
