Sources close to the Russian group AAR say it is exploring a sale of its 50 percent stake in TNK-BP, a joint venture with BP, which could be worth $30 billion or more by some estimates. (Karen Bleier/AFP/Getty Images)

The Russian partners in a fractious joint venture with BP say that they are willing to sell their half of TNK-BP.

Sources close to the Russian group AAR say it is exploring a sale of its entire 50 percent stake, which could be worth $30 billion or more by some estimates. The Russian partners also are considering selling their interest in a public offering.

The Russian partners disclosed their intention to explore these options in a letter to BP.

The move comes as BP, frustrated by bickering for several years, is negotiating to sell its half of TNK-BP to the Russian oil giant Rosneft. BP’s sale would likely be for a combination of cash and stock, increasing its existing stake in Rosneft.

Earlier, BP had offered to buy out AAR’s half of TNK-BP but the Russian partners said no. Now, AAR says it will try to sell its stake if Rosneft buys out BP, saying that Rosneft lacks BP’s expertise.

A sale by BP to the politically well-connected Rosneft could weaken the position of the Russian partners, though sources close to AAR said AAR has a good relationship with Rosneft.

“This notion gives us additional flexibility including an IPO or a disposal option, which may be a way to optimize returns for shareholders,” said Stan Polovets, chief executive of AAR.

Last year, AAR blocked BP from entering a venture with Rosneft to explore Russia’s Arctic region because AAR said the terms of the TNK-BP joint venture required BP to do that through the joint venture. Exxon Mobil ended up stepping in.

In addition, BP and its Russian partners have been unable to agree on the size of the 2012 dividend from TNK-BP. Since 2003, the lucrative joint venture has paid out $19 billion to BP.