China's Lenovo and NEC Corp of Japan said on Monday they expect to lift their combined market share in Japan's PC market by about 5 percent in three years through their joint sales venture.

Lenovo, the world's No.4 PC brand, is hungry for alliances to help widen razor-thin margins, while NEC, Japan's biggest PC name, longs for a toehold in global markets to lift its 0.8 percent market share worldwide.

Lenovo and NEC have yet to work out how the partnership will affect product development and costs, or exactly how it will lift the two firms' combined 25 percent share of a shrinking market.

NEC holds technologies especially for Japan that could be leveraged around the world, Roderick Lappin, head of Lenovo's Japan business told reporters at a news conference, but said that nothing concrete had been decided.

Foreign players such as Hewlett-Packard have tried to break into Japan, the world's third biggest PC market, but have failed to loosen the grip of local companies such as Fujitsu Ltd and Toshiba Corp.??

Research firm IDC Japan forecasts a 9.2 percent decrease in Japan's PC market to 14.3 million units in 2011, and says the market shrank by 16.1 percent in January-March after the March 11 quake hurt corporate IT spending.

Tablet PCs are revolutionizing the sector, with some analysts predicting Apple Inc as likely to replace HP as the No.1 notebook vendor globally in 2012, if tablets are included in sales totals.

Lenovo holds 51 percent of NEC Lenovo Japan, with the rest belonging to NEC, which has the option to sell that stake to Lenovo after five years.

(Reporting by Mayumi Negishi; Editing by Joseph Radford)