This article has been updated to include Iliad’s confirmation of the offer.

Small French carrier Iliad  is offering $15 billion for a 56.6 percent stake in T-Mobile, Reuters confirmed.

Iliad owner Xavier Niel said the deal represents a 42-percent premium over T-Mobile’s stock price at the time of the announcement. Iliad confirmed the deal already has backing from international banks.

Sprint’s stock has fallen nearly six percent as of 11:15 a.m. CT upon news of the offer. The U.S.’s third largest carrier, owned by Japanese carrier SoftBank, is widely speculated to be putting together a merger bid for T-Mobile that values the carrier at around $32 billion.

Reuters recently reported a transaction announcement could come in September as Sprint negotiates with Deutsche Telekom, the German carrier that owns 67 percent of T-Mobile.

Sprint and SoftBank have run into resistance from U.S. regulators reluctant to further consolidate the U.S. wireless industry’s current four-competitor landscape.

Iliad believes regulators will look more favorably on its offer for T-Mobile since the French carrier does not currently operate in the U.S.