LONDON -- Americans Jake Gibb and Sean Rosenthal were knocked out of the Olympic beach volleyball tournament on Monday night by Latvia.

The Americans won the first set 21-19, then dropped two straight to Martins Plavins and Janis Smedins, 21-18, 15-11.

The other American men's team, Beijing gold medalists Todd Rogers and Phil Dalhausser, had already been eliminated.

Latvia will meet the reigning world champion Brazilian team of Emanuel and Alison, which escaped a set point in the third to beat Poland 21-17, 16-21, 17-15.

The United States is already guaranteed a medal in the women's bracket, with two-time gold medalists Kerri Walsh-Jennings of San Jose and Misty May-Treanor into the semifinals along with April Ross and Jennifer Kessy.