By Christoph Steitz and Andreas Rinke
FRANKFURT/BERLIN (Reuters) - Uniper is weighing legal proceedings before a Swedish arbitration court to claim billions of euros in compensation from Gazprom over what it says are unjustified gas supply cuts, two people familiar with the matter said.
Germany's largest importer of Russian gas posted a 12.3 billion euro ($12.3 billion) first-half loss and had to be bailed out by the state after reduced supplies from Gazprom forced it to buy replacement volumes at higher prices.
The Stockholm arbitration court, where the sources say Uniper would seek the claims, has repeatedly dealt with gas contract quarrels between Gazprom and its counterparts, including Poland's PGNiG and Ukraine's Naftogaz.
The most high-profile corporate victim of Europe's energy crisis so far, Uniper earlier this year said that it was reviewing legal steps against Gazprom and that this could include arbitration proceedings.
Such proceedings usually take several years before a verdict is reached.
"Of course Uniper will ... examine such damage claims against Gazprom and, if there is a strong prospect of success, try to enforce them," Uniper, which is majority-owned by Finland's Fortum, said in emailed comments.
Gazprom, which currently sends no gas via the Nord Stream 1 pipeline after flows had already been reduced since June, declared force majeure with regard to gas deliveries, a view Uniper rejects.
Uniper has said that reduced supplies from Gazprom, which had been its single-biggest supplier, brought the company to the verge of collapse and were the chief reason for a government bailout that has grown to 19 billion euros.
($1 = 0.9987 euros)
(Reporting by Christoph Steitz and Andreas Rinke; Editing by Miranda Murray and Bernadette Baum)