The United States now moves on to the medal round, where they'll face defending champion Cuba in the first round Wednesday.
Kao was working on his third inning of relief in the ninth when catcher Brian Peterson doubled. After second baseman Brant Ust struck out, Milledge shot a single through the left side of the infield, plating Peterson with the eventual deciding run.
Milledge is hitting .270 (10-for-37) with three home runs and five RBI in eight games for Team USA. His former Mets minor league teammate, right-hander Brian Bannister, is 1-1 with a 6.52 ERA in two starts.