The healthcare specialist and WeissComm Partners will jointly 'pursue global business opportunities and preferentially refer leads to each other'.
WeissComm is jointly headed by Jim Weiss and Diane Weiser; its headquarters are in San Francisco and it also has an office in New York. It has a similar number of staff to Resolute's 28.
Weiser previously worked with Resolute founders and joint MDs Anna Korving and Paul Blackburn at Ketchum, where they were chiefs of the New York and London healthcare practices respectively.
Weiss, meanwhile, has held senior comms roles at firms such as Genentech, Rhone-Poulenc Rorer and Heartport.
The deal is the latest move by Resolute to bolster its international capability. Just over two months ago it unveiled the hire of US healthcare PR veteran Phil Sheldon, who has joined as a board director (PRWeek, 18 March).
The agencies provided an undisclosed Resolute client with 'issues management support' at a US congress last year.