Boston tech giant Hale and Dorr is in merger talks with Washington DC’s Wilmer Cutler & Pickering in a deal that promises to forge a national US giant with an annual turnover of more than $700m (£382m).

The proposed deal, which is expected to be closed within a matter of weeks, would represent the biggest US tie-up since the 2001 merger between Chicago’s Sidley & Austin and New York’s Brown & Wood.