* Talks ongoing for several weeks about trade finance deal
* Rosneft needs over $40 bln to buy TNK-BP, invest in projects
* Deal would give majors, traders long-term access to Russian oil
By Dmitry Zhdannikov and Melissa Akin
LONDON, Dec 13 (Reuters) - Russia's Rosneft is talking to oil majors and traders including Shell, Total and Glencore to raise up to $10 billion, using future oil exports as collateral, to complete its purchase of TNK-BP and become the world's biggest listed oil producer.
Such trade finance is usually the least preferred option for oil firms, as they like to keep their export flows free from obligations, but the $55 billion acquisition of TNK-BP, a joint venture between BP and Soviet-born billionaires, will most likely be testing banks' exposure limits for one borrower.
Five sources close to Rosneft and the potential lender companies told Reuters that talks between Rosneft and its traditional oil buyers such as Royal Dutch Shell, Total , Glencore and Vitol had been going on for several weeks, with Rosneft collecting proposals on the amount of money and terms from the companies.
Sources said the list of lenders could also include BP, which may be keen to facilitate an end to its often fractious TNK-BP partnership.
Rosneft did not immediately respond to requests for comment.
Rosneft, headed by Igor Sechin - a close ally of President Vladimir Putin - needs to borrow up to $40 billion to complete the TNK-BP acquisition and is already talking to banks to raise over three quarters of that in what would be Europe's ninth-biggest syndicated loan.
Rosneft also needs money to launch new fields in Russia's Arctic and finance a $25 billion refinery modernisation programme.
Among its financing options, the sources said Rosneft wants to raise up to $10 billion from oil majors and traders.
"It will easily be one of the biggest ever trade finance deals. It will certainly dwarf anything Rosneft has done to buy YUKOS," said a source familiar with the discussions.
Rosneft bought most of the assets of private oil firm YUKOS at state-forced auctions in the middle of last decade. To buy YUKOS, Rosneft borrowed heavily via syndicated loans, eurobonds and trade finance deals, but most of those trade finance export-backed deals have already expired or are about to expire.
"Rosneft has now most of its export flows free and ready to be collateralised again," another source said.
Sources said so far Rosneft has had very preliminary commitments from some majors and traders ready to contribute between $500 million and $3 billion each, with the total still being below $10 billion.
Talks have so far focused on terms such as maturity and pricing, which include commitments to supply oil.
"Rosneft says deals could last for up to five years. Pricing proposals are a bit funny. Rosneft says, 'Give us the money and we will sell you crude at prices close to spot tenders that we will continue to hold'. So I'm wondering where is my upside?" one source involved in talks said.
A source close to Rosneft disagreed.
"(The upside is in) control of the flow. This is a natural hedge, so you can trade around it," the source said.
Rosneft regularly sells crude at spot tenders, and the latest tenders have been dominated by trading houses Vitol and Glencore, which outbid previous winners such as Shell by offering very high premiums.
"Europe's oil market will be on edge over this deal and who wins access to crude. People are getting a bit tired of the Vitol/Glencore current dominance," a source at one major said.
To pay back $10 billion, Rosneft would need to sell 125 average-size Urals crude cargoes, according to Reuters calculations. Split over five years, it would represent only two cargoes a month, a fraction of Rosneft's monthly sales of around 30 tankers.
BP will also hold around 20 percent of Rosneft as part of the deal to sell its half of TNK-BP.
"Because BP will be a big stakeholder in Rosneft, it is not so obvious for them to also be on the lender and oil buyer side because of a potential conflict of interest," one source said. (Reporting by Dmitry Zhdannikov and Melissa Akin; Editing by Will Waterman; Editing by Will Waterman)