* Iliad bid $15 bln for 56.6 pct of T-Mobile US at $33/share
* BNP, HSBC agree to lend up to $13 billion - sources
* Iliad shares fall as analysts question wisdom, cost of bid
* Shares in French rivals fall as consolidation hopes fade
* Sprint has head start, higher offer for T-Mobile (Adds investor comments, updates shares)
By Leila Abboud and Arno Schuetze
PARIS/FRANKFURT, Aug 1 (Reuters) - Telecoms group Iliad has lined up BNP Paribas and HSBC to finance its bid for T-Mobile US, people familiar with the matter said, as it pursues a deal that could overturn expectations of industry consolidation in both the United States and France.
Shares in Paris-based Iliad dropped as much as 13 percent on Friday, as analysts questioned the wisdom and cost of its surprise $15 billion offer for 56.6 percent of T-Mobile US , the No.4 U.S. mobile operator.
Shares in rival French companies Bouygues and Orange also fell on speculation that Iliad's interest in a U.S. deal meant it might not seek a tie-up at home that could ease competition in a cut-throat market.
"The offer may even not be meant absolutely seriously," said Frank Heise, fund manager at Metzler Asset Management and an owner of Iliad shares. "Iliad wants to exert pressure on the players in France. It wants to show Orange and Bouygues that it can go it alone and does not necessarily need them."
In the United States, Iliad is also jeopardising an expected consolidation and faces a potential bidding war for T-Mobile US with No.3 operator Sprint, and its Japanese backer Softbank.
Iliad, which is being advised by Lazard banker Vincent Le Stradic on its offer, said on Thursday there could be no certainty its bid for T-Mobile US, 66.7 percent owned by Deutsche Telekom, would be accepted.
Sprint and Softbank have been in talks with T-Mobile for months and agreed in June to a framework of a deal that values the company at roughly $40 per share, sources earlier told Reuters.
Iliad's offer represents a lower price of $33 per T-Mobile share, and $36.20 if the buyer delivers on $10 billion of promised costs savings it thinks it can generate from running the carrier more efficiently.
But Iliad, which is majority owned by billionaire founder Xavier Niel, believes its bid faces fewer antitrust issues than Sprint's, so Niel thinks he has an advantage in the talks, sources close to the matter said.
The Paris-based broadband and mobile provider said on Thursday its bid would be financed in debt and equity.
HSBC and BNP have committed to lending up to $13 billion to Iliad, said one person familiar with the situation. HSBC is also acting as Iliad's adviser.
Niel would put in up to 1 billion euros of his own money, said the person, and a share sale to raise up to 2 billion euros would be done at the Iliad level.
Debt would be raised by Iliad, at the level of a 100 percent owned holding company below Iliad, as well as by T-Mobile US.
"Debt will be raised at three levels overall. The deal will stand or fall on the financing," said the person.
"Can Xavier Niel pull it together? It's a very large leveraged deal. It has a lot of similarities to Numericable's successful bid for SFR in France in terms of structure."
With many U.S.-based banks already conflicted given that they have signed onto the Sprint-Softbank bid, their international rivals HSBC and BNP embraced the chance to finance the Iliad approach.
Five global banks - JPMorgan Chase & Co, Goldman Sachs Group, Deutsche Bank AG, Bank of America Merrill Lynch and Citigroup Inc - have agreed to finance Sprint's proposal to buy T-Mobile, sources told Reuters in June.
In bidding for T-Mobile US, Iliad is taking aim at a target much bigger than itself. Iliad's market capitalisation was just above $16 billion before Friday's share drop, compared with about $25 billion for T-Mobile US.
Iliad has 8.6 million mobile customers and 5.7 million in broadband, and generated 2013 sales of 3.75 billion euros, or $5 billion. T-Mobile US has 50 million mobile customers and 2013 revenue of $24.4 billion
David Moss, head of European equities at F&C, who does not own Iliad shares, cast doubt on Iliad's ability to win the deal.
"There are no synergies. They've come up with 10 billion but we don't know where that's come from," he said. "Shocked, surprised, bemused are the words that come to mind."
Metzler Asset Management's Heise was cautiously optimistic.
"Iliad has shown in France that it can roil a market with its low cost base. But that may not work so fast and easily in the U.S., where the market conventions are different: higher average revenue per customer, different product packages, more promotion expenses," he said.
THREAT TO CONSOLIDATION
Shares in rival French telecom companies fell on Friday as investors eyed the implications of Iliad - potentially a catalyst for consolidation among the four mobile players there - looking elsewhere for growth, leaving the industry at home to suffer continued erosion of margins and cut-throat competition.
France has been in the throes of a price war since 2012 sparked by Iliad's Free Mobile brand, which has sent prices down by one-third.
Third-place mobile carrier Bouygues has become the main target after losing out in a bidding war in April to buy bigger rival SFR to cable group Numericable. Its shares were down 4 percent. Former monopoly Orange's shares were down 2 percent, while Iliad's stock had pared its losses by 1255 GMT to trade down 5 percent.
Iliad made an informal offer to buy Bouygues earlier this year, and also took part in talks with Orange about a joint bid for Bouygues, sources told Reuters. Bouygues rejected these overtures on grounds the prices being floated were too low.
(1 US dollar = 0.7468 euro) (Additional reporting by James Regan in Paris, Simon Jessop in London, and Gwenaelle Barzic in Paris; Editing by Andrew Callus and Mark Potter)