MILAN, March 28 (Reuters) - A consortium led by Italian state lender CDP is set to send Atlantia a sweetened offer for its stake in Autostrade per l'Italia in a last-ditch attempt to salvage talks over the fate of the motorway business, three sources said.

CDP, together with co-investors Macquarie and Blackstone, have been negotiating with Atlantia on Autostrade since last year to try to end a dispute triggered by the 2018 collapse of a bridge ran by Autostrade per l'Italia.

The CDP is expected to decide on the revised offer for 88% of Autostrade at a board meeting late on Sunday.

The new bid, yet to be finalised as talks continued, still values all of Autostrade at 9.1 billion euros ($10.73 billion) but makes some concessions, the sources familiar with the matter said.

Macquarie and Blackstone declined to comment.

The consortium is considering offering Atlantia a lower level of exposure to potential legal claims compared with the offer proposed in February, which called on the group to pick up the first 1.5 billion euros in claims should they materialise, they added.

The investors are also willing to allow Atlantia keep subsidies Rome is expected to grant Autostrade this year as part of support offered to companies to buffer the impact of the coronavirus.

Atlantia would get the lion's share of some 400 million euros that would be available to the company under the support scheme by the time the deal closes, which is expected to be in the second half of 2021, two of the sources said.

Atlantia, controlled by the Benetton family through holding Edizione, owns 88% of Autostrade, with the rest held by Germany's Allianz and funds DIF, EDF Invest and China's Silk Road Fund.

Both Edizione and another key investor, banking foundation CRT, said earlier this week the CDP-led bid appeared to be the best option for the sale of Autostrade.

Atlantia's board is expected to discuss the new offer at a meeting on Wednesday or Thursday, one source said.

($1 = 0.8477 euros) (Reporting by Giuseppe Fonte, Stephen Jewkes, Francesca Landin. Writing by Agnieszka Flak. Editing by Jane Merriman)