Boaz Weinstein, the founder of activist firm Saba Capital, has once again raised his bid for publicly listed asset manager Sculptor Capital Management, which has an agreement in place to sell itself to Rithm Capital.

Over the weekend, Weinstein and his partners presented a takeover proposal of around $13 per share, up from an earlier $12.76-per-share bid, according to media reports. Weinstein is backed by Pershing Square Capital Management’s Bill Ackman, Avenue Capital Group’s Marc Lasry and Susquehanna International Group’s Jeff Yass.

Real estate investment firm Rithm, which in July agreed to acquire Sculptor for $11.15 per share, or $639 million, is considering raising its own offer given Weinstein’s push, the reports add. That agreement with Rithm raised the ire of Sculptor founder Daniel Och and other former executives, including ex-CEO Rob Shafir, who have suggested Sculptor should do a deal with Weinstein.

So far, Sculptor has rejected Weinstein’s overtures, raising several issues about a potential transaction with the activist investor. Weinstein would have the “ultimate decision-making authority over investments,” Sculptor warned in a proxy statement last month, adding that some of its clients are worried about Weinstein’s clout after the takeover.

Under his latest offer, Weinstein agreed to complete the transaction even if all investors in Sculptor’s two hedge fund strategies oppose it, though other company clients are still required to give their consent. Rithm’s proposal allows it to back out if more than 15% of Sculptor clients, as measured by fees paid, reject the deal.

Shares in Sculptor, which manages more than $30 billion, gained 6.3% in after-hours trading Tuesday after losing nearly 2% during regular hours.