(Reuters) - Sprint Corp is meeting with banks to work out funding for its bid for smaller rival T-Mobile US Inc, a source familiar with the situation said, as the mobile carrier works to ease regulatory concerns that the deal would hurt competition.

The source said that Sprint, which is owned by Japan's SoftBank Corp, is hoping to fund the bulk of T-Mobile's estimated $50 billion price tag with corporate bonds and cover the rest with syndicated loans and convertible bonds.

Sprint is currently talking to at least five banks, the source told Reuters, including JP Morgan, Goldman Sachs and Deutsche Bank.

Bloomberg, which first reported that Sprint was in talks with banks on Thursday morning in Asia, said the carrier was also talking to Mizuho Financial Group Ltd and Citibank. Softbank is expected to make a formal offer in June or July, Bloomberg added.

Sprint spokeswoman Roni Singleton told Reuters the company does not comment on rumors and speculation. T-Mobile and SoftBank both declined to comment on the Bloomberg report.

Sprint is facing a battle ahead with U.S. regulators who oppose consolidation in the wireless market on the basis it would inhibit competition. The company is aware it may have to give up some of its spectrum holdings to win over critics, the source said.

Two of the most vocal opponents to the deal are Federal Communications Commission Chairman Tom Wheeler and U.S. antitrust chief William Baer, who have pointed to T-Mobile's success since U.S. authorities rejected a 2011 merger between AT&T Inc and T-Mobile on the grounds the market needs at least four major players to be competitive.

The failure of that deal cost AT&T a $6 billion break-up fee, a penalty Sprint feels confident it can avoid, the source said, adding that it is leaning towards having Deutsche Telekom, which currently owns 67 percent of T-Mobile, retain part of that stake.

SoftBank chief executive Masayoshi Son is lobbying regulators by arguing his purchase of a second U.S. mobile operator would break up a cozy oligopoly dominated by AT&T and Verizon Communications Inc, pointing to the price war he initiated when he took over Vodafone's failing Japanese operation eight years ago.

T-Mobile has a market cap of $23.52 billion, according to Thomson Reuters data