Locke Liddell & Sapp, based in Houston and Dallas, and Chicago-based Lord, Bissell & Brook have agreed to merge and will form a 700-lawyer firm named Locke Lord Bissell & Liddell.

Jerry Clements, the Austin, Texas-based managing partner of Locke Liddell, says the firms signed a preliminary term sheet on Tuesday. The merger must be approved by at least 75 percent of the partners in each firm at votes set for mid-July and is expected to close by Aug. 1.