Bryan Cave and Squire Sanders & Dempsey are expected to seal their merger in the next month after partners at both firms received merger packs with details of the new management team last week.
Sources at the firms expect partners to vote on the merger within the next fortnight.
As first reported by The Lawyer (30 January), St Louis-based Bryan Cave and Ohio-headquartered Squire Sanders have been in merger talks for months.
Upon completion the merger would create a firm with a turnover of $808.5m (£436.7m) and more than 1,400 lawyers.
Both firms have been encouraging integration between its lawyers with events such as the recent Bryan Cave golf day, which was attended by Squire Sanders partners.
Squire Sanders has a history of growing through merger. Earlier this year it took the entire London office and a team in Frankfurt from the now defunct Haarmann Hemmelrath.
Last September Squire Sanders fought off a dozen firms to secure a merger with Miami-based Steel Hector & Davis, which gave the firm a strong presence in Latin America.
However, in the run-up to the merger, Squire Sanders lost its 60-lawyer Madrid office to DLA Piper Rudnick Gray Cary in December.
A Squire spokesman denied knowledge of any talks.