PARIS, Jan 17 (Reuters) - French waste and water management company Suez, which is fighting a takeover approach from arch-rival Veolia, said on Sunday it has received an alternative proposal from investment firms Ardian and Global Infrastructure Partners that could lead to a bid.

Suez has for months been trying to fight off Veolia , which is now its main shareholder with 29.9%.

Ardian and Global Infrastructure Partners (GIP) had shown interest in the past, but this is the firmest sign yet of Ardian's intent to produce an offer, at 18 euros per share - the same price proposed by Veolia - which values Suez at 11.3 billion euros ($13.65 billion).

Suez CEO Bertrand Camus said the potential offer from Ardian/GIP did not create uncertainties about jobs or raise antitrust problems, unlike the bid by Veolia.

"It's the implementation of a friendly solution ... with scenarios that could be different, but that could lead to an offer for all of it (Suez)," Camus told reporters in a conference call.

Veolia said in a statement that its 29.9% stake in Suez was not for sale.

Ardian and GIP said in a separate statement that they supported a move to "strengthen two great French champions of environmental services", rather than see them merge.

Veolia last year bought a chunk of Suez from French utility Engie in a prelude to a takeover offer for the whole group that has been contested by Suez managers and led to legal challenges from both sides.

Camus said France was better equipped with two water and waste management firms rather than one.

Veolia earlier this month sent its offer proposal to the Suez board, saying it intended to file for the 70.1% of the company's capital it does not own.

By taking over Suez, Veolia aimed to expand its reach globally in a highly fragmented industry. ($1 = 0.8277 euros) (Reporting by John Irish, Gwenaelle Barzic and Sarah White; Editing by Hugh Lawson and Susan Fenton)