* Minority shareholders say the offer is low
* Rosneft says the offer will last 75 days
* Concerns about the treatment of minorities in Russia
MOSCOW, Nov 6 (Reuters) - Russian state oil company Rosneft said on Wednesday it could delist shares in TNK-BP Holding, which it acquired last year, if its offer to buy out minority shareholders falls through.
The ultimatum ups the stakes in a tussle between Rosneft and the TNK-BP minority investors that followed Rosneft's $55 billion takeover in March of the Anglo-Russian oil venture TNK-BP. The deal left investors owning 5 percent of TNK-BP's listed business feeling short-changed.
Rosneft CEO Igor Sechin, an ally of President Vladimir Putin, originally declined to offer to buy out minority owners of TNK-BP Holding, later renamed RN-Holding.
In September, Rosneft offered them 67 roubles ($2.06) per ordinary share and 55 roubles per preferred share.
But the offer disappointed some investors who had hoped to get closer to the $3.70 a share that a quartet of tycoons led by Mikhail Fridman were estimated to have received in the TNK-BP deal, Russia's largest ever takeover.
On Wednesday, Rosneft said it would proceed with its initial offer, saying it would be effective for the next 75 days, until Jan. 20.
"Even if Rosneft is unable to complete, or decides not to proceed with such a buyout, Rosneft intends to seriously consider the possibility of delisting RN-Holding," Rosneft said in a regulatory filing.
This got a chilly response from minority shareholders who include local and international investment funds focused on eastern Europe.
"The threat to delist RN-Holding is new. I still think the offer is very low," one RN-Holding minority shareholder told Reuters on condition of anonymity.
Emerging markets fund manager Mark Mobius has appealed for Rosneft to make a "fair and equitable" offer to buy out minority shareholders in TNK-BP and has sought a meeting with Sechin.
Rosneft had told Reuters earlier that it was unable to confirm the reports about a meeting. A Rosneft source has confirmed that Mobius had written a letter to Sechin.
Russian stocks trade at a near 50-percent valuation discount to those of other emerging nations, reflecting foreign investors' worries over a range of issues including corruption, corporate governance and stalled efforts to modernise the economy.
($1 = 32.5515 Russian roubles) (Reporting by Vladimir Soldatkin and Katya Golubkova. Editing by Jane Merriman)