* Rothschild seeks to counter Bakrie plan to unwind Bumi
* Says investors committed $342.5 mln in possible new equity
* They account for over quarter of voting rights -sources
* Bumi Plc board meets on Wednesday
By Clara Ferreira-Marques
LONDON, Dec 10 (Reuters) - Financier Nat Rothschild said he had secured the support of 11 investors including Abu Dhabi, Schroders and Standard Life as he seeks to counter efforts by his former partners in Bumi to dismantle the coal mining venture.
Rothschild has been battling Indonesia's politically influential Bakrie family since they announced a $1.4 billion bid in October to buy back operating assets they had brought to the venture, effectively unwinding Bumi and bringing months of shareholder tension to a head.
Hedge fund veteran Rothschild, who founded Bumi with the Bakries two years ago, resigned from the board days later in order to fight the proposal. He has since been rallying new and existing investors, hoping to revive the venture and his deal-making reputation along with it.
"My understanding is that the thresholds required by the Bakries to see their proposal succeed cannot now be reached," he said in a statement.
A Bakrie spokesman could not be reached for comment. Bumi confirmed it had received a letter from Rothschild but did not comment further.
Bumi's shares have fallen more than 75 percent since June last year, hit by falling coal prices, shareholder battles and a probe into allegations of wrongdoing at the group's Indonesian operations.
Detailing a letter sent to Bumi's board last week, Rothschild said the investors had committed to injecting fresh cash into Bumi - a total of $342.5 million including Rothschild's own commitment to put in $75 million.
Sources familiar with the matter said that including Rothschild's own 12 percent shareholding, those supporting his bid accounted for some 27 percent of Bumi's voting rights, potentially a minority strong enough to block the Bakrie move.
The 11 investors include five top institutional shareholders in Bumi: Abu Dhabi Investment Council, which is the investment arm of the Abu Dhabi government, and fund managers Schroders, Standard Life Investments, Taube Hodson Stonex and Artemis.
Other investors supporting him include mining entrepreneur Robert Friedland and Indonesian investor Hashim Djojohadikusomo, owner of the Arsari group of companies and brother of former general and current presidential candidate, Prabowo Subianto.
In Rothschild's alternative proposal, Bakrie-supporting shareholders would be bought out, while Bumi would keep some coal assets, namely majority-owned Berau Coal.
He said in the letter to Bumi's board that the investors were ready to put up cash to "remove completely the Bakries and their allies from the Bumi Plc shareholder register".
Bumi Plc's board meets on Wednesday.