WASHINGTON, Dec 23: The United States on Thursday criticized Moscow's move to take over the main asset of oil giant Yukos, saying the lack of transparency in the process could hurt Russia's standing in the world economy.

"We're disappointed in the way this case has been handled," deputy State Department spokesman Adam Ereli told reporters after the Russian state petroleum company Rosneft acquired Yukos' core oil-pumping subsidiary, Yuganskneftegaz.

"We certainly don't think it's been disposed of in a transparent or open way," he said. "We think this sends the wrong signals to foreign investors and could negatively impact Russia's role in the global economy."

Russian President Vladimir Putin on Thursday defended the state's takeover of Yukos' main assets because it failed to pay its taxes. He said the state, through state oil company Rosneft, had acted legally and used "absolutely legal market mechanisms".

Mr Ereli said the United States wanted to see investment and trade flourish in Russia but Moscow had to make sure its operations were all above board. "We think it's important that they act to ensure those who are watching developments in Russia ... that some of the institutional weaknesses and questions raised by this case are addressed in ways that restore confidence in Russian institutions."

Rosneft became the new owner of Yuganskneftegaz after buying the mystery firm that had won a secretive weekend auction for the massive Siberian concern, owner of 17 per cent of Russia's vast oil reserves.

Rosneft, which is already merging with state-run gas monopoly Gazprom to create a national oil and gas corporation, issued a surprise announcement saying it had acquired 100 percent of the shares of previously unknown Baikalfinans group.

Despite voicing its displeasure with the conduct of the deal, the United States remained determined to work for Russia's admittance into the World Trade Organization, Mr Ereli said. But he added: "Obviously it's part of that process (that) issues of transparency and accountability and predictability need to be addressed."

HEADQUARTERS SEARCHED: Russian police on Thursday again searched the headquarters of the Yukos oil group. The search was carried out "in the framework of the criminal investigation into the non-payment of taxes by companies controlled by the Yukos group", said a spokesman for the state prosecutor. -AFP