T-Mobile US Inc. plans to turn down Iliad SA’s $15 billion deal proposal, two people with knowledge of the matter said, putting pressure on the French telecommunications company to raise its offer.

Iliad, which has offered $15 billion in cash for 56.6 percent of T-Mobile, is seeking possible partners to help finance its bid, and allow it to make an offer for a larger stake, another person said, asking not to be named discussing private information. These could include telecommunications companies as well as financial and sovereign investors, this person said.

Iliad’s $33 a share offer, made last week, came amid Sprint Corp.’s efforts to acquire all of T-Mobile. Sprint and T-Mobile are the No. 3 and No. 4 carriers in the U.S. and their combination will face the scrutiny of regulators who are seeking to preserve four competitors in the U.S. market. Iliad, led by billionaire founder Xavier Niel, raises few of the same regulatory concerns because it doesn’t currently have a U.S. presence.

T-Mobile rose 1.8 percent to $34.30 as of 3:15 p.m. in New York today. Sprint fell 1.9 percent to $7.25 a share.

Deutsche Telekom AG, which holds 67 percent of T-Mobile, considered Iliad’s initial bid as inferior to Sprint’s, a person familiar with the matter said last week. The Bonn-based carrier’s management would consider missing out on a higher price if that meant avoiding the uncertainty of a prolonged antitrust review, other people said.

The German company wants to avoid reliving its 2011 attempt to sell T-Mobile to AT&T Inc. for $39 billion. The accord was blocked by the U.S. Federal Communications Commission and the Department of Justice.

Stretched Finances
Iliad’s shares fell the most in almost eight years the day after it disclosed its bid, amid concern that the company, valued at 11 billion euros ($15 billion), would stretch its finances too thin in a bidding war for T-Mobile.

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Bellevue, Washington-based T-Mobile has almost twice Iliad’s market value and may have to spend billions of dollars on spectrum and network construction in coming years.

Anne Marshall, a spokeswoman for T-Mobile, declined to comment. Iliad spokeswoman Isabelle Audap declined to comment.

Iliad’s effort to find a partner to help increase its bid was earlier reported by Reuters.