MOSCOW, March 21 (RIA Novosti) - ConocoPhillips will invest up to $3 billion this year to increase its stake in Russia's largest privately-owned oil company, its chairman told a leading Russian newspaper Tuesday.

John Malva told Vedomosti that Conoco, which currently owns almost 17% of Lukoil shares, will invest an additional $2.5-$3 billion by yearend to bring its stake to 20%, the ceiling set by bilateral agreements with the Russian company.

Conoco and Lukoil (LKOH.RTS) are working on projects in the Timan Pechora oil and gas basin in northeastern European Russia, and also in Iraq's Western Qurna oilfield, Malva said.

ConocoPhillips is also looking to join Gazprom in developing the vast Shtokman gas field off Russia's Arctic coast, he said. The Russian natural gas monopoly, currently selecting foreign partners for its Shtokman project from a shortlist including Conoco and four other companies, said it would unveil its picks before April 15. The other companies in the running are U.S. giant Chevron, Norway's Statoil and Norsk Hydro, and France's Total.

Malva said Conoco could invest billions of dollars into the project's first phase.

The Shtokman deposit, located 650km from the Barents Sea port of Murmansk, holds an estimated 3.2 trillion cu m of natural gas and 31 million metric tons of gas condensate.