NEW YORK (AP) — Arkhouse Management and Brigade Capital Management are upping their offer to acquire Macy's in a deal now valued at $6.6 billion.

The investment firms announced Sunday that they had submitted an all-cash proposal of $24 for each of the remaining shares in Macy's they don't already own — up from a earlier offer of $21 per share.

Macy's rejected the previous deal, which was valued at $5.8 billion, in January. At the time, the retailer said that its board reviewed the investment firms’ proposal and not only had concerns about the financing plan, but also felt there was a “lack of compelling value.”

In a joint-statement Sunday, Arkhouse managing partners Gavriel Kahane and Jonathon Blackwell said that they "remain frustrated by the delay tactics" from Macy's board and its “continued refusal to engage" — but were still committed to completing the transaction.

Kahane and Blackwell added that they had repeatedly tried to address the company's concerns, and were open to increasing the purchase price more “subject to the customary due diligence.”

Macy's on Sunday confirmed that it had received the “revised, unsolicited, non-binding” proposal. The New York-based company said that its board would carefully review the offer, and that it did not intend to comment further until the evaluation was complete.

Last month, Arkhouse moved to nominate nine people for Macy’s board. Macy’s at the time said it had been seeking additional financing information — but that Arkhouse instead sent a letter requesting that the company extend its director nomination window by 10 days.

Arkhouse, meanwhile, said it had provided additional financing details and that the firm requested the deadline extension in hopes of continuing to engage privately. Since that request was rejected, Arkhouse added, the firm nominated directors.

On Tuesday, Macy's announced it would close 150 namesake stores over the next three years including 50 by year-end after posting a fourth-quarter loss and declining sales. As part of restructuring efforts, the department store chain also said it would upgrade its remaining 350 stores.