The two cities, Calgary and Stockholm are the only three definite candidates to host the event, and a decision is due in June.
"We are leaving Rome and Italy very confident about this candidature, because we can really see things coming together," Bach told reporters in a news conference at Italian Olympic Committee (Coni) headquarters.
Bach said he had discussed Italy's bid on Wednesday with Sports Minister Giancarlo Giorgetti, who "expressed the support of the government, which is ready to deliver the guarantees on security".
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Argentina's Olympic Committee has said it was considering a late run, but Bach seemed unwilling to consider the possibility. "We will not change the rules of the race", he said, when asked about last-minute candidacies.
The original Italian bid put together Milan, Cortina and Turin but collapsed in September because of divisions between the three city halls. The government then said it would not back any alternative proposals, but Milan and Cortina pushed ahead alone.
Coni President Giovanni Malago said he had spoken on Wednesday with the two cities and the regional governments of Veneto, which surrounds Cortina, and Lombardy around Milan, to set up a working group to manage the bid.
The fate of Calgary's bid will be decided by a non-binding plebiscite on Nov. 13, after the Olympic assessment committee recommended the city scrap its plans over a funding row with the Canadian federal government.
Stockholm's candidacy also looks precarious because it does not have the backing of Sweden's main political parties.
(editing by Gavin Jones and John Stonestreet)
