PARIS — After more than five months of negotiations, Etihad Airways of Abu Dhabi confirmed on Sunday that it was nearing an agreement that could lead to a sizable investment in Alitalia.

In a joint statement, the airlines said Etihad would formally submit a letter to Alitalia’s board in the coming days detailing the conditions of a nonbinding offer for a stake of up to 49 percent of the money-losing Italian airline, which received a 500 million euro, or $682 million, government-led bailout late last year.

“We are delighted to be able to move forward with this process and look forward to the successful conclusion of the proposed transaction with Alitalia,” said Etihad’s chief executive, James Hogan.

Neither airline would discuss the terms of Etihad’s planned offer or comment on recent Italian media reports about the deal. Those reports have suggested that Etihad is prepared to pay as much as €560 million for the stake, which under the European Union’s rules on airline ownership must be capped at 49 percent.