* Highest ranking exec to leave since shareholders fell out
* BP may sell TNK-BP stake to Rosneft, AAR may stay or sell
* Dodds unlikely to join colleagues at Rosneft
* Deputy seen as likely successsor
MOSCOW, Oct 11 (Reuters) - The head of upstream at Russian oil firm TNK-BP will leave the company, the highest-ranking executive to depart in an exodus of staff as a potential sell-off by its main shareholders looms, sources close to TNK-BP said on Thursday.
Alexander Dodds joined TNK-BP from ExxonMobil Qatar, where he had served as president, in October 2011. The sources said his resignation would be announced to company staff on Friday.
Senior TNK-BP staff, including its top oil trader and head of mergers and acquisitions, have left the company in the months since BP and its partners in the Russian-British oil company said their 50-50 joint venture was untenable.
Both sides have said they are willing to sell out, though the quartet of Soviet-born billionaires who share control of the No.3 Russian oil producer have also said they would be willing to buy out the British oil major.
Russian state-backed oil firm Rosneft has said it would like to buy out BP and is seeking financing for the deal, likely to be worth a total of $25 billion or more, though a full merger of TNK-BP and Rosneft through a buyout of both partners could be difficult to finance.
Dodds is seen as unlikely to join a steady flow of executives from TNK-BP and BP itself to Rosneft, however. Sources close to TNK-BP said his likely successor was his deputy, Nikolai Ivanov.