Japanese telecom giant SoftBank - which owns Sprint - is reportedly looking at T-Mobile US for a merger. This would be the second attempt after 2014's approach was rebuffed by US regulators.

According to Reuters, which broke the story, Japan's SoftBank is prepared to give up control of Sprint Corp to Deutsche Telekom's T-Mobile US Inc to clinch a merger of the two U.S. wireless carriers. Following the news, the entire sector is bid on the news, even AT&T.

As Reuters details, SoftBank has not yet approached Deutsche Telekom to discuss any deal because the U.S. Federal Communications Commission has imposed strict anti-collusion rules that ban discussions between rivals during an ongoing auction of airwaves.

After the auction ends in April, the two parties are expected to begin negotiations, the sources told Reuters this week.

Two and a half years ago, SoftBank abandoned talks to acquire T-Mobile for Sprint amid opposition from U.S. antitrust regulators. That deal would have seen Deutsche Telekom retain a minority stake in T-Mobile, down from about 65 percent.

Deutsche Telekom Chief Executive Tim Hoettges has said in recent months that the German company is no longer willing to part with T-Mobile, prompting SoftBank to explore a new strategy to achieve a potential combination, the people said.

SoftBank, which owns about 83 percent of Sprint, has been frustrated with its inability to grow significantly in the United States on its own, where both Sprint and T-Mobile have struggled to compete with Verizon Communications Inc and AT&T Inc, the two largest U.S. carriers with much deeper pockets.

Investors have said a merger between T-Mobile and Sprint, ranked third and fourth respectively, would still face antitrust challenges, but made strategic sense as the industry moves to fifth-generation wireless technology. Carriers will need to spend billions of dollars to upgrade to 5G networks that promise to be 10 times to 100 times faster than current speeds.

While SoftBank is still open to discussing other options, it is now willing to surrender control of Sprint and retain a minority stake in a merger with T-Mobile, the sources said. They asked not to be identified because the deliberations are confidential.

SoftBank, Sprint, Deutsche Telekom and T-Mobile all declined to comment.

How big would the deal be?

Reuters could not determine how much of a premium SoftBank may want Deutsche Telekom to pay for control of Sprint, which has a current market valuation of $36 billion. T-Mobile's market value stands at $50 billion, which is about $20 billion higher than when it was last in merger talks with Sprint in 2014.

While Sprint's market value has changed little since then, T-Mobile has overtaken Sprint as the No. 3 wireless customer in terms of numbers of subscribers. T-Mobile said it had 71.5 million total customers while Sprint had 59.5 million at the end of 2016.

Barclays analysts wrote in a note in December that a merger of T-Mobile and Sprint could result in $25 billion to $30 billion in synergies but said, "it is not imminently clear to us that the various regulatory agencies would reverse course having already blessed the outcome of a four-player market."

"We may buy, we may sell. Maybe a simple merger, we may be dealing with T-Mobile, we may be dealing with totally different people, different company," SoftBank Chief Executive Masayoshi Son told analysts on the company's latest quarterly earnings call earlier this month, presumably hoping the Trump administration is more amenable than Obama's.