T-Mobile US Inc. 's second-quarter results easily topped analysts' expectations as the fourth-biggest wireless operator said it gained more than 1.5 million subscribers during the period.

The results come as bidders begin to circle T-Mobile, which is majority-owned by Deutsche Telekom AG and locked in a fight for subscribers with industry leaders Verizon Communications Inc. and AT&T Inc.

SoftBank Corp. 's Sprint Corp., the third-largest wireless carrier in the U.S., has long been expected to make an offer for T-Mobile, and The Wall Street Journal has reported that a deal announcement could come this summer.

But French upstart telecommunications company Iliad SA is trying to counter that move and submitted its own offer less than a week ago to T-Mobile's board, The Journal reported Thursday. The contours of that offer and the response, if any, from T-Mobile are unclear.

A merger between T-Mobile and Sprint would likely result in a lengthy regulatory review, as officials have indicated they would oppose the move as it reduces customers' choices.