Bingham McCutchen has agreed to merge with Washington DC's Swidler Berlin, in a move that will give the leading national firm a 200-lawyer practice in the US capital.

As first reported on legalweek. com (8 December), Bingham has signed a letter of intent to integrate the 140-lawyer Swidler with its 53-lawyer local branch in the first quarter of 2006, creating a top 20 US law firm with a turnover of more than $700m (£399m).

The two firms previously considered a tie-up a few years ago, although various factors including conflicts with Swidler's energy and insurance practice made a deal difficult. However, following the departure of the vast bulk of Swidler's New York branch for Dechert in January, Bingham and Swidler re-started discussions in October.

The DC firm is best known for its respected bankruptcy practice, also a key practice area for the 850-lawyer Bingham. Swidler clients include Global Crossing, Adelphia, GE, Ford and Georgia-Pacific.

Bingham chairman Jay Zimmerman commented: "This merger will give us a stronger presence in Washington DC – an area of particular strategic importance to the firm – and further enhance our national platform. Based upon our discussions to date, we are optimistic about bringing this transaction to completion."

The two firms still have to complete due diligence, conflict review and a partner vote, but a successful tie-up would make the DC office Bingham's second-largest, after its Boston hub.

Last year, Swidler Berlin held merger talks with Orrick Herrington & Sutcliffe, before the bulk of the firm's New York practice left for Dechert.

It is the latest major deal among America's bulging band of national practices, which includes this year's tie-up between Squire Sanders & Dempsey and Steel Hector & Davis, and last year's formation of Wilmer Cutler Pickering Hale and Dorr.

Bingham itself has been actively pursuing domestic mergers, having forged recent deals with Los Angeles-based Riordan & McKinzie, 300-lawyer Californian firm McCutchen Doyle Brown & Enersen and New York's Richards & O'Neil.