Citigroup Inc. will help arrange a $10 billion loan to OAO Gazprom, Russia's biggest company, to finance the state-owned gas producer's purchase of a controlling stake in OAO Sibneft, bankers involved in the deal said.

Citigroup, the No. 1 U.S. financial services company, was added to the group of arranger banks after offering lower rates than lenders led by ABN Amro Holding NV and Dresdner Kleinwort Wasserstein, said the bankers, who declined to be identified. The two European banks were forced to match Citigroup's price on what may rank as Russia's biggest loan.

Citigroup, the largest foreign bank in Russia, slid to fourth place in the $25 billion market for Russian loans, bonds and stocks this year from No. 1 in 2004, according to data compiled by Bloomberg. The bank has been operating in Russia since 1993 and has 1,500 employees and 1,200 corporate clients in the country.

Michael Klein, head of investment banking at Citigroup, met with Gazprom Chief Executive Alexei Miller at the company's Moscow headquarters and discussed the ``prospects of joint work in securing financing,'' Gazprom said on Aug. 23. New York-based Citigroup hasn't arranged a loan for Gazprom since at least 1999, according to data compiled by Bloomberg.