PFF Bancorp Inc. said Monday that it has agreed to be acquired by FBOP Corp., for $1.35 in cash for each share of PFF Bancorp common stock, a deal that values the bank company at about $31 million.

The offer represents a 14 percent premium on PFF’s closing price of $1.18 on Friday. Oak Park, Ill.-based FBOP, which is the parent company of California National Bank, said it expects the deal to close by the end of September.

Rancho Cucamonga-based PFF said its board unanimously approved the merger and has recommended that the company’s stockholders approve the deal.

In order to ensure PFF remains its “adequately capitalized” regulatory status, FBOP will loan the bank $7 million in exchange for a secured note that’s convertible into preferred stock with voting rights equivalent to 19.9 percent of outstanding shares.

Shares in PFF added 7.6 percent to $1.27 in early trading Monday. Shares in PFF are down 87 percent since the end of March.