Russian billionaire Mikhail Prokhorov's investment group Onexim has joined a list potential bidders for a stake in potash producer Uralkali, as the search continues for a peacemaker to end a row that has soured relations with Belarus.

Tycoon-turned-politician Prokhorov was linked by Bloomberg on Wednesday to the stake owned by his former partner Suleiman Kerimov, who has come under pressure after Uralkali in July quit a sales cartel with state-owned Belaruskali that had controlled two-fifths of the world market.

The dissolution of the pact threatens to push prices down 25 percent, a massive blow to the fragile economy of Belarus which relies on exports of potash, a major fertilizer ingredient, for 12 percent of state revenue.

Uralkali CEO Vladislav Baumgertner has been in a KGB prison in Minsk for nearly a month, and faces up to 10 years in jail on charges of abuse of office, raising pressure for a change of ownership that could bring about a reconciliation.

Kerimov is not under pressure to sell, one financial source familiar with his position said, but a search is under way for a buyer acceptable to the Kremlin who would be able to "pour oil on troubled waters".

Prokhorov, a metals and banking tycoon who owns the Brooklyn Nets pro basketball team, ran against Vladimir Putin in last year's presidential vote but is widely seen as a card-carrying member of Russia's establishment.

Onexim declined to comment, as did Kerimov's investment company, Nafta.

Kerimov owns a 21.75 percent stake in Uralkali through his foundation. Together with his partners, Filaret Galtchev and Anatoly Skurov, he controls 33 percent of Uralkali.

Three sources familiar with the matter told Reuters that nothing had been decided so far, with one adding: "Everybody is going around in circles."

Two of the sources said Kerimov and his partners wanted a premium for the asset, while the potential buyers were seeking a guarantee that good relations with Belarus would be restored.

"It's an attempt to organise a beauty contest," one said.

Chinese sovereign wealth fund China Investment Corp acquired a 12.5 percent stake in Uralkali, via a bond exchange deal on Tuesday. The deal was triggered when Uralkali's market value fell below $20 billion, a level that could serve as a benchmark for future deals.

Analysts say the Chinese deal, on behalf of a country that is the world's top potash importer, might complicate attempts to revive the Russia-Belarus potash cartel

Join The Queue

Prokhorov joins a roll-call of candidates that have been linked in press reports to Uralkali, including Norilsk Nickel , the Arctic miner run by Vladimir Potanin - another former partner. Norilsk has denied any interest.

Also linked to the stake has been Vladimir Evtushenkov, majority owner of telecoms-to-oil conglomerate Sistema.

Evtushenkov has also denied his interest and, in an interview on Wednesday, CEO Mikhail Shamolin told Reuters that Sistema was not considering any offers.

Political contacts between Moscow and Minsk have intensified this week, with Russian President Vladimir Putin meeting his Belarussian counterpart Alexander Lukashenko on the fringes of a regional summit on Monday.

Prime Minister Dmitry Medvedev told reporters on Wednesday he would discuss the matter with his Belarussian opposite number, Mikhail Myasnikovich.

It was Myasnikovich who invited Baumgertner to a meeting on Aug. 26 after which the Uralkali CEO was detained, triggering public protests by the company's chairman, former Kremlin chief of staff Alexander Voloshin.

"(We) will (discuss) everything, of course, definitely," Medvedev told reporters in Astana, the capital of Kazakhstan.