According to published reports, former Maine Sen. George J. Mitchell, a partner in the law firm of Piper Rudnick in Washington, is becoming chairman of the third-largest legal firm in the world.

Piper Rudnick was to merge Jan. 1 with DLA, the seventh-largest law firm in Britain. Piper, with about 1,000 lawyers, has its roots in Baltimore.

The combined firm, to be called DLA Piper Rudnick Gray Cary, at least to start, will have 49 offices in 18 countries, almost 2,500 lawyers and revenues of about $1.5 billion a year. The U.S.-British pairing follows a trend of U.S. firms merging with foreign firms to make following clients with global aspirations easier.

Since leaving the U.S. Senate, Mitchell brokered a peace agreement in Northern Ireland and is serving as chairman of Walt Disney Co.