Aug 20 (Reuters) - Hedge fund firm Sculptor Capital Management said on Sunday it has received an unsolicited bid from a third party that had participated in a strategic alternatives process, but the bid did not show "adequate committed funding."

Sculptor, which last month agreed to be acquired by Asset manager Rithm Capital for $639 million, had been exploring a sale since last year, amid a legal battle with its founder Daniel Och.

Rithm had said that it would pay $11.15 per class A share of the hedge fund.

The latest bid's headline valuation is higher than the Rithm transaction, but the proposal only includes committed financing for less than half of the amount required for the transaction, Sculptor said in a statement, adding that the offer underestimates the amount that would be necessary by "several hundred million dollars."

A special committee "has not determined that the bid is, or is reasonably expected to lead to, a superior proposal," the hedge fund said, without naming the third party.

The Wall Street Journal reported on Sunday that investors Boaz Weinstein, Bill Ackman and Marc Lasry have made a rival offer for Sculptor.

Weinstein's group presented an offer for Sculptor that was rejected during the sale process and it has subsequently increased its bid to more than $12 a share, people familiar with the matter told the Journal.

Ackman's Pershing Square Capital Management declined to comment.

Weinstein's Saba Capital Management and Lasry's Avenue Capital Group did not immediately respond to Reuters' requests for comment. (Reporting by Kanjyik Ghosh in Bengaluru; Editing by Muralikumar Anantharaman and Sonia Cheema)