"MOSCOW, July 18 (RIA Novosti) - Russia's migration authorities have extended the visa of Robert Dudley, the CEO of Russian-British joint oil venture TNK-BP, until July 29, a Federal Migration Service (FMS) spokesman said on Friday.

Dudley's current visa expires on July 19. The BP-appointed American executive of TNK-BP, Russia's third largest oil producer, has been at the center of a dispute between its British and Russian shareholders over strategy, management, and control of the company. The Russians have demanded Dudley's dismissal, saying he has acted only in the interests of BP.

"His application has been approved. Robert Dudley's visa has been extended for 10 days until July 29," the spokesman said, declining to comment further on the decision.

The FMS demanded on Wednesday a copy of Dudley's new contract with TNK-BP before issuing him a new visa. The migration authorities said his labor contract had expired, and that a new visa could not be issued without a valid contract.

BP reacted by saying that Russia had no grounds to deny Dudley a visa.

"Mr. Dudley has a legally valid employment contract and a work permit in place. His positions as CEO of TNK-BP and Chairman of the Management Board of TNK-BP Management remain in force," the company said on its website.

However, a key Russian shareholder and chairman of the board of directors of TNK-BP Management confirmed in a letter to the FMS chief published on Thursday that Dudley's contract expired on January 1, 2008 and had not been extended since.

"The Board of Directors of TNK-BP Management has not elected or considered electing a management board chairman, or signed a labor contract with him in the specified period," Viktor Vekselberg said.

Speaking at a news briefing in Moscow on Thursday, Dudley said he would not give in to Russian shareholders' demands to resign, as he feels responsible for the company and wants to ensure it survives the current dispute, while retaining its potential for growth.

TNK-BP, in which the British oil major and a holding owned by four Russian tycoons control 50% each, has been hit by tax and labor checks recently, raising concerns that the company's foreign staff could be forced to leave Russia. In early July, however, migration authorities said they would issue most requested work permits for foreign staffers.