Shares of T-Mobile and Sprint climbed for the second time this week after the companies reportedly reached “a major breakthrough” in merger negotiations.

Reuters and CNBC reported Sprint parent SoftBank would own 40% to 50% of the combined carrier, while Deutsche Telekom, which owns T-Mobile, would claim a majority stake. “A deal is expected by the end of October,” according to the report, which cites unnamed people familiar with the talks, although there’s a chance it could still fall through.

Shares of Sprint rose more than 3% in pre-market trading this morning on the news; T-Mobile’s stock was up more than 1% before the market opened.

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CNBC reported earlier this week that the two parent companies “have been in frequent conversations” regarding a stock-for-stock tie-up that would see Deutsche Telekom become the majority owner of the combined carrier. T-Mobile CEO John Legere would lead that company, according to earlier reports.

The election of President Donald Trump coupled with the conclusion of the FCC’s incentive auction several months ago has given rise to a flurry of speculation regarding potential M&A activity in the mobile market. And much of that talk has centered on some kind of merger between the nation's two smaller major wireless carriers.

SoftBank spent more than $20 billion to acquire Sprint in 2012, and the company had hoped to acquire T-Mobile as well, merging the carriers to take on Verizon and AT&T. That effort was dropped when U.S. regulators indicated they were opposed to a merger, however.

Analysts say a deal would make sense in several ways. The carriers’ spectrum holdings are complementary—T-Mobile is in the process of expanding its coverage through the 600 MHz airwaves it recently won at auction, while Sprint sits on an enormous pile of 2.5 GHz spectrum that T-Mobile openly covets—and the move would result in three dominant network operators of similar size. Meanwhile, T-Mobile’s momentum over the last three years is undeniable, and Sprint continues to struggle to gain its financial footing even as it gains market share.

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“We continue to believe 1) a deal makes sense both strategically and financially (at the right price of course), and 2) the current regulatory environment seems to provide the best window to attempt a transaction,” Barclays said in a research note earlier this week. “Whether both operators can get to a meeting of the minds on whether an attempt makes sense is of course the critical first question. Moreover, whether that deal gets approved remains the next question. We can see a path forward, but ultimately it comes down to whether the respective parties can.”