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UPDATE 2-SoftBank-owned Fortress to make rival bid for Japan's Unizo -Nikkei

* H.I.S has launched 3,100 Y/shr offer to raise Unizo stake to 45%

* Unizo opposes H.I.S. offer, sought Fortress as 'white knight'-report

* Unizo says in talks with a potential partner (Adds Unizo comment)

TOKYO, Aug 16 (Reuters) - Fortress Investment Group, a U.S. investment firm owned by SoftBank Group, will offer to buy Japanese hotel operator Unizo Holdings, launching a counter bid against travel agency H.I.S. Co, the Nikkei reported.

Fortress will a launch tender offer as soon as the start of next week for all the shares in Unizo at a price higher than H.I.S.'s offer of 3,100 yen per share, the Nikkei said on Friday.

Unizo, which opposes H.I.S.'s bid, has sought help from Fortress as a 'white knight', the Japanese daily said, without citing sources.

Following the Nikkei report, Unizo said in a statement it was in talks with a potential partner and would hold a board meeting on Friday, without commenting further on the report.

Fortress declined to comment. H.I.S. representatives were not immediately available for comment.

H.I.S., which already owns 4.79% in Unizo, last month launched a tender offer to raise its stake in Unizo to as much as 45%. Unizo said it opposed the offer, setting the stage for a rare hostile bid in Japan.

Unizo has a stock market value of about 123.5 billion yen ($1.2 billion), according to Refinitiv data.

U.S. hedge fund Elliott Management has been gradually raising its stake in Unizo and now holds 9.9% of the hotel operator, regulatory filings show.

Unizo shares closed at 3,600 yen on Thursday, or 16% above H.I.S.'s offer. Trading was suspended following the Nikkei report. ($1 = 106.0600 yen) (Reporting by Chris Gallagher; Additional reporting by Antoni Slodkowski and David Dolan; Editing by Richard Pullin and Muralikumar Anantharaman)