Russian oil firm TNK-BP could sell the huge Kovykta gas field in Russia to state holding company Rosneftegaz by the end of 2010, a key shareholder said.

Viktor Vekselberg, a billionaire TNK-BP shareholder, said the deal could amount to between $700m and $900m, reports Reuters.

In 2007, TNK-BP agreed to sell Kovykta to Gazprom, but the deal was deferred repeatedly due to disagreements over price.

Development of the field has been held up for years amid threats that TNK-BP’s licence would be revoked for failing to start full-scale production.

The field has gas reserves of 1,300 billion cubic metres and is strategically located to supply China.

Rosneftegaz owns stakes in Gazprom and Russia’s biggest oil company, Rosneft.