Studio Santa Maria, the Italian ally of Kramer Levin Naftalis & Frankel, has sidelined the New York firm to form an alliance with Greenberg Traurig.
The deal sees 40-lawyer Studio Santa Maria abandon its seven-year relationship with Kramer Levin and instead form an exclusive relationship with Greenberg Traurig, the Miami-based giant which boasts 22 offices across the US.
There is no suggestion of a full merger at this stage.
The termination of the alliance with Kramer Levin also heralds the end of formal ties between UK firm Berwin Leighton Paisner (BLP) and the Italian firm, although Studio Santa Maria head Luigi Santa Maria said BLP would remain its UK firm of choice.
BLP insisted that its relationship with Studio Santa Maria would not be affected by the US developments.
Luigi Santa Maria was formerly foreign counsel in Kramer Levin's New York office, but is returning to Italy to become foreign counsel with Greenberg Traurig.
The move coincides with the opening of Greenberg Traurig's six-lawyer Italian desk, based in the firm's 270-lawyer New York office and led by former Wachtell Lipton Rosen & Katz senior associate Lorenzo Borgogni.
Greenberg Traurig's head of European development Richard Rosenbaum said the link-up was aimed at exploiting practice synergies between the two firms, namely in IP, brand protection, litigation, government and corporate.
Greenberg Traurig is perhaps best known for its election work for the Bush administration, while Studio Santa Maria is recognised for its big-ticket litigation and M&A expertise.