* Rhoen says B. Braun seeks shareholder vote on deal
* Rhoen says will seek to close the deal regardless
* B. Braun not available for comment (Adds details on court case, background on dispute)
FRANKFURT, Nov 21 (Reuters) - German hospitals chain Rhoen-Klinikum said on Thursday that shareholder B. Braun Melsungen AG has filed a lawsuit to contest the sale of hospitals, which account for about two-thirds of Rhoen's revenues, to Fresenius SE.
Fresenius tried to take over Rhoen last year but failed after B. Braun and another shareholder blocked it. In September, Fresenius agreed to buy about two thirds of Rhoen's assets in a deal it claims does not require shareholder approval.
Rhoen said on Thursday it remained convinced that the deal does not require shareholder approval.
"This lawsuit cannot be successful," said Rhoen Chairman and founder Eugen Muench, who last year initiated the proposed sale of the entire group, in which he and his wife hold 12.5 percent.
Rhoen in September agreed to sell most of its hospitals to diversified healthcare group Fresenius for 3.07 billion euros ($4.1 billion), in an attempt by Rhoen's Muench to outflank the opponents to an outright sale of the company.
B. Braun, owned by the family of Ludwig Georg Braun, competes with Fresenius in hospital equipment, such as intravenous and tube feeding supplies.
The company, which last month raised its stake in Rhoen-Klinikum to an 11 percent blocking minority, was concerned it would lose Rhoen as a major client should Fresenius take it over.
Rhoen said the plaintiff was seeking to have the hospitals deal declared void or to summon a shareholder meeting to vote on the matter.
Rhoen said, however, it would continue to work towards closing the deal regardless.