Mayer Brown, in response to recent published reports that it was discussing a possible merger in London, acknowledged Tuesday that it has had preliminary talks with English firm Simmons & Simmons. But the Chicago law firm said the discussions have ended without any agreement.

In a joint statement, the two firms said, “Mergers are complex and present a number of issues which need to be resolved before discussions can proceed.  We have concluded that a combination between our firms is not the right option.”Such a combination would have created one of the world’s largest law firms, with more than 2,500 lawyers.

Mayer Brown has a large presence in London with 340 lawyers. Most of them joined the firm in 2002, when Mayer Brown merged with English firm Rowe & Maw. But the office suffered a blow last year when the head of the practice left over disagreements with the Chicago management team.

Apparently, Mayer Brown sees more room for growth in London, one of the world’s most lucrative legal markets with large financial-services firms that rival those in New York. Cross-Atlantic mergers are gaining steam. Chicago’s Sonnenschein Nath & Rosenthal recently tied the knot with U.K.’s Denton Wilde after the merger of Hogan & Hartson and Lovells.

Simmons & Simmons has about 900 lawyers, less than one third of the size of London’s largest, most prestigious firms.

Mayer Brown is the tenth largest firm in the U.S. based on its $1.1 billion in revenue in 2009, according to American Lawyer magazine.