LONDON, Dec 30 (Reuters) - Global commodities trader Trafigura has completed the purchase via a wholly-owned subsidiary of a 10% stake in Rosneft's Vostok Oil project in the Arctic, the company said on Wednesday.

"The acquisition is majority financed by long-term debt financing provided to the entity," Trafigura said in a statement without disclosing the figure paid.

The Geneva-based trader bought the stake through a subsidiary called CB Enterprises Pte Limited and the deal is its largest upstream interest. Earlier this year, the company bought a minority stake in London-listed President Energy. However, trading firms typically prefer to stay asset-light and favour production prepayment deals rather than holding equity.

As part of the deal, Trafigura will have long-term access to oil supplied from the major oil basin. Rosneft has estimated the oil and gas condensate resources to be 6 billion tonnes (44 billion barrels).

Earlier this month, Trafigura CFO Christophe Salmon likened the area to the prolific Permian Basin in the United States and a supply opportunity that could not be ignored.

Rosneft is also talking to other trading companies and oil firms about prefinancing for Vostok, according to three sources familiar with the talks.

Vostok Oil was formed to unite Rosneft's projects in northern Russia, including the Lodochnoye, Tagulskoye and Suzunskoye oilfields and other projects, including the Ermak Neftegaz venture with BP.

Sources close to the talks with Rosneft have said the project has been valued at over $70 billion.

The project will have to develop pipelines, roads, a sea port and other infrastructure. Crude oil is expected to be shipped to Asia via the North Sea Route (NSR). (Reporting by Julia Payne and Dmitry Zhdannikov, editing by Louise Heavens and David Evans)