TOKYO (Reuters) - Japan's SoftBank Corp will hold a news conference on Tuesday about its deal to acquire 70 percent of U.S. wireless carrier Sprint Nextel Corp as investors seek clues on whether it might trump a counteroffer from Dish Network Corp.

SoftBank's billionaire founder and top executive Masayoshi Son, who has remained tight-lipped on Dish's bid for Sprint, will brief the media from 5 p.m. (0800 GMT) in Tokyo after releasing its full-year financial results.

The Japanese mobile operator announced a $20.1 billion deal for the majority stake in Sprint last October as it looks for growth abroad. The company faces a stagnating market at home, crowded by large competitors such as NTT DoCoMo Inc and KDDI Corp.

SoftBank has said it is on track to close its deal with Sprint by July 1.

The Japanese company received support for the deal from Intel Corp Chief Executive Paul Otellini, who wrote to the Federal Communications Commission saying Son's vision to build a high-speed U.S. national network was compelling.

"We need this competition in the wireless space as the ATT/Verizon model is not giving that to consumers at this time," Otellini said.

U.S. satellite TV provider Dish has offered $25.5 billion for Sprint, aiming to tap the company's wireless network to offer services that would let U.S. consumers watch video anywhere, anytime.

Sprint said on Monday that SoftBank has waived some terms of their agreement so that Sprint can seek more information from Dish.

Analysts and sources say Son is unlikely to walk away from Sprint, with SoftBank's lenders open to providing additional financing if the company decides to raise its bid.

Sprint has set June 12 as the tentative date for a special meeting for shareholders to vote on the proposed deal with SoftBank.

SoftBank's shares were up 0.9 percent on Tuesday afternoon at 4,815 yen, compared with a 0.2 percent dip in Tokyo's benchmark Nikkei average. Although the shares lost nearly one-fourth of their value in the two days after the Sprint deal was announced, they have since rebounded and are up 67 percent since that time, in line with the Nikkei's 62 percent surge.

(Reporting by Mari Saito; Editing by Edmund Klamann)