The firms have reached an agreement to merge, pending approval by partners at each firm, the two firms said on Sunday.

The new combined entity—Allen Overy Shearman Sterling—will boast more than 3,900 lawyers worldwide.

The move comes after Shearman’s merger talks with Hogan Lovells fell through earlier this year. The deal gives UK-founded Allen & Overy a much larger footprint stateside, as some of London’s top firms also seek to boost their presence in the US.

“We have listened to our clients and their requests for the highest quality advice to help navigate the demands they face, and to do so in an integrated and globally consistent way,” Wim Dejonghe, Allen & Overy’s senior partner, said in a statement. “We, A&O Shearman, will do this by accelerating our ability to bring the best of both firms, regardless of geography.”

The firms referred to the combination as a merger, rather than an acquisition by Allen & Overy. They have not determined who will lead the combined firm, they said, adding that leadership will be shared by officials from each firm.

Allen & Overy is by far the larger of the two firms, with more than 3,000 lawyers around the globe. It brought in nearly $2.7 billion in gross revenue last year and more than $2.4 million in profits per equity partner.

Shearman had more than 700 lawyers last year, per American Lawyer data. The firm tallied more than $1 billion in gross revenue over the year and more than $3 million in profits per equity partner.