MILAN, Oct 19 (Reuters) - Italian state lender CDP is trying to put together a proposal on Monday to buy Atlantia's 88% stake in motorway business Autostrade per l'Italia along with two big international funds, three sources close to the matter said.

CDP's investors - Italy's Treasury and a group of banking foundations - are expected to give their nod to the plan on Monday and final approval is expected later in the day when CDP's board is due to meet, the sources said.

Presentation of the proposal by CDP in a consortium with investment funds Macquarie and Blackstone could mark a turning point in long-running negotiations between Atlantia and the government.

The group has been embroiled in a legal dispute with Rome since 2018, when a bridge run by Autostrade collapsed killing 43 people. The government has threatened to strip Autostrade of its motorway licence.

The two parties had moved closer to a deal in July, when Rome approved a plan under which Atlantia would cede control of Autostrade to CDP, but negotiations to finalise the project floundered.

Last week, CDP and Atlantia began exclusive talks to try to break the deadlock.

The plan under discussion would involve CDP having 40% of the consortium, while Macquarie and Blackstone each would have 30%, two sources said.

CDP could then sell on part of its stake in the motorway business to Italian investors at a later stage.

The sources said talks were still ongoing and how much the deal would be worth was still under discussion.

Bank of America analysts have estimated the equity value of Atlantia's stake in Autostrade at 9 billion euros ($10.58 billion). CDP's offer may include a price adjustment mechanism to account for some damage claims for Autostrade, two sources have said.

Atlantia's board is to meet at 1600 GMT, sources said. ($1 = 0.8504 euros) (Reporting by Francesca Landini, Stephen Jewkes, Stefano Bernabei. Editing by Jane Merriman)