* May then exit through an IPO, sale to strategic investor
* VTB with partners get 55 pct, Rostelecom 45 pct
* Merger to strengthen No. 4 player (Adds detail, background, VTB comments)
MOSCOW, Feb 6 (Reuters) - Russian bank VTB said it would stay for at least three years as an investor in T2 RTK Holding, the country's No.4 mobile carrier being formed from the merger of Tele2 Russia and the wireless assets of Rostelecom .
State-controlled VTB bought Tele2 Russia from Nordic telecoms group Tele2 for $3.6 billion last April.
It later agreed to sell half of the business to a group of investors including affiliates of Bank Rossiya and entities of Alexei Mordashov, a billionaire tycoon who controls steelmaker Severstal.
And last year, Tele2 Russia, already the country's No.4 mobile operator, decided to merge with the wireless assets of Rostelecom, aiming to close the gap on MTS, Megafon and Vimpelcom which together control more than 80 percent of the Russian mobile market.
"This is a strategic project for us and a relatively long-term investment for all the shareholders. The minimum term we are looking at to develop the company is likely three years," said Yuri Soloviev, VTB's First Deputy President, as the two operators signed a framework agreement to press ahead with the merger.
The bank may then exit T2 RTK Holding through an initial public offering or sale to another investor, he told reporters during a conference call.
VTB and its partners will get a 55 percent stake in T2 RTK Holding, with Rostelecom having 45 percent. Soloviev said that Rostelecom could raise its stake in the future - through a possible public share offering or if one of the partners sells.
Rostelecom approved the spin-off of its mobile business, including several operators and voice and data licences, last year, but will have to buy out shareholders that did not support the move.
Soloviev said VTB could help Rostelecom to finance the buyout, but denied an earlier report in the Kommersant newspaper that it might purchase shares in Rostelecom.
Analysts have said it remains to be seen whether an enlarged No.4 player will be able to defend its position and grow in the short term. Tele2 sold out of Russia because it did not see strong enough growth prospects after failing to secure 3G and 4G data licences.
T2 RTK Holding will form a board of directors and hold a meeting on strategy this month, Soloviev said. He added a decision on who will be the CEO had yet to be taken. (Reporting by Oksana Kobzeva and Maria Kiselyova; Editing by Megan Davies and Mark Potter)