Rosneft oil trading unaffected by U.S. sanctions - traders

* Sanctions bar new debt of longer than 90 days maturity

* Sanctions will "spur" Russia's modernisation - Rosneft chairman

By Vladimir Soldatkin

MOSCOW, July 17 (Reuters) - Oil trading operations at Russia's top oil company Rosneft will not be hurt by new U.S. sanctions, with deals usually coming in below the cut off point of a 90-day maturity, traders and analysts said on Thursday.

The penalties could have an impact on Rosneft's cooperation with foreign firms on large projects and procurement, they said, but it was not yet clear whether they would or to what extent.

President Barack Obama imposed sanctions on Rosneft, Russia's second largest gas producer Novatek and its third largest bank Gazprombank on Wednesday over what Washington says is Moscow's reluctance to curb violence in Ukraine.

The sanctions in effect close medium- and long-term dollar funding, the Treasury Department said. U.S. companies are only prohibited from engaging in any "new debt of longer than 90 days maturity or new equity" with the energy firms and banks.

Traders and analysts said trade financing, required to cover Rosneft's trading operations, comes in well below that period.

"It appears that there is no immediate effect on operations, because Rosneft's and Novatek's operating interaction with U.S. companies is limited; oil sales are mostly routed via traders. Rosneft's contracts' duration is below 60 days," Julia Pribytkova, a senior analyst at Moody's Investors' Service in Moscow, told Reuters.

"We are not aware of either company planning to tap capital markets in the near term. However, we are looking at the broader effect on the international cooperation on major projects, and potential implications for the procurement of equipment."

Rosneft's shares fell by over 4 percent as of 1040 GMT, wiping around $1 billion off market capitalisation on the back of the announced sanctions.

Rosneft's crude oil exports account for a half of some 200 million tonnes (4 million barrels per day) of Russia's annual exports. The company offers more that 15 million tonnes of crude oil at its semi-annual "jumbo" tenders.

"Trade finance at the semi-annual tenders is 30 days. (Sanctions) will not influence it at all," said a trader.

A spokesman for Rosneft declined immediate comment, while its chairman, Alexander Nekipelov, said sanctions would in fact help "spur" Russia's modernisation, according to Itar-Tass news agency.

"ILLEGAL" SANCTIONS

Rosneft's head Igor Sechin, a long-standing ally of Russian President Vladimir Putin, called the U.S. sanctions on the Kremlin-controlled company illegal because it had played no role in Ukraine.

Rosneft, which accounts for 40 percent of Russian oil output, the world's largest, offers heavy volumes of oil and oil products for traders. It is also in the process of acquiring Morgan Stanley (Xetra: 885836 - news) 's oil trading unit.

Last year, Rosneft announced deals worth more than $15 billion to sell crude oil and other products to BP (LSE: BP.L - news) , which now owns almost a fifth of Rosneft following Rosneft's $55 billion acquisition of Anglo-Russian oil firm TNK-BP last year.

Last month, Rosneft also agreed to supply BP with 12 million tonnes of refined oil products. The deal involves a pre-payment of at least $1.5 billion arranged by leading global financial institutions for Rosneft, which refined 90 million tonnes (1.8 million barrels per day) of oil products last year.

BP said the sanctions appear on first glance to focus on restricting access of targeted firms to medium and long-term U.S. financing.

Analysts say Rosneft is still facing borrowing difficulties after becoming heavily indebted following the TNK-BP deal. It needs funding to service its debt, which is estimated to be at 1.7 times annual earnings before interest, taxes, depreciation, and amortization (EBITDA).

Analysts at Alfa bank said a lot would depend on how long the sanctions would last and whether they might be tightened.

"The timeframe for these sanctions is rather unclear, though we do understand that they depend heavily on the ongoing violence along Ukraine's border with Russia," they said in a note.

"The closure of external debt markets to the company would seriously jeopardise its large-scale investment plans, including brownfield output maintenance, East Siberia oil greenfield development, refining modernisation and boosting gas output to 100 billion cubic metres by 2020." (Additional reporting by Gleb Gorodyankin; editing by Philippa Fletcher)