Norton Rose Fulbright is in merger discussions with United States firm Chadbourne & Parke.
Sources have reported that merger negotiations have been taking place between the two firms for several months and have now reached advances stages, with an announcement from the firms on their prospective tie-up expected imminently.
The tieup would create a firm well into the top ranks by turnover. Norton Rose's turnover past year stood at £1.1bn; Chadbourne & Parke £198m.
The firms happen to share the same office building in NY at 1301 Sixth Ave, where Chadbourne signed a 20-year lease in 2012 and moved into space vacated by failed firm Dewey & LeBoeuf.
Neither firm responded to a request for comment. These were followed by a second Canadian merger with Calgary's Macleod Dixon in 2012, while legacy Norton Rose's union with United States firm Fulbright & Jaworski went live in summer 2013.
Earlier this month, worldwide firm Eversheds' merger with US-based Sutherland Asbill & Brennan went live, creating a global firm with combined revenue of more than £600m.