The Wall Street Journal says Iliad is trying to snap up T-Mobile before it's sold to Sprint, the No. 3 U.S. cellphone carrier. That deal has been rumored for a long time, but has not been announced.
Analysts believe U.S. regulators are likely to block the T-Mobile/Sprint pairing due to concerns that it would reduce competition.
Iliad is much smaller than T-Mobile US, and the Journal said it was bidding only $16 billion. T-Mobile US's market capitalization was $25 billion before the stock shot up 4.3 percent in midday trading, after the paper's report.
Iliad and T-Mobile US had no immediate comment.