New York firms Dewey Ballantine and LeBoeuf Lamb Greene & MacRae have agreed to merge to form a 1,300-lawyer firm.
Dewey has shrugged off its failed merger with Orrick Herrington & Sutcliffe in January to enter into a combination with LeBoeuf that, if successful at a partner vote, will go live in October. The new firm will be known as Dewey & LeBoeuf.
The merged firm will have a revenue of just under $1bn (£500m) and operations in 12 countries. It will be headed by current LeBoeuf chairman Steven Davis.
While cultural differences between Orrick and Dewey were often quoted as the main stumbling block between those two firms, Dewey and LeBoeuf share a similar ethos and history.
The firms' average profit per equity partner (PEP) figures are also broadly similar – $1.45m (£730,000) at Dewey and at $1.43m (£720,000) at LeBoeuf.
Dewey co-chairman Mort Pierce said: "Dewey Ballantine has been focused on growth for some time and this combination with LeBoeuf Lamb is an especially good fit. LeBoeuf Lamb brings a practice and industry focus that complements and enhances our areas of practice to create a powerful array of offerings for clients."
The tie-up will see the merged firm have 550 lawyers in New York, while it will be the fifth largest US firm in London, boasting a presence of 170 lawyers.