Mardy Fish has given the United States a 1-0 lead in its Hopman Cup match against Denmark after rallying to beat Frederik Neilsen 4-6, 7-6 (5), 6-4.
Fish broke Neilsen when the Dane was serving for the match at 6-5 in the second set to force the tiebreaker.
Fish was originally scheduled to play the second match of the series, but organizers switched the order of the men's and women's singles matches because top-ranked Caroline Wozniacki only arrived in Perth earlier Monday.
Wozniacki was set to play American Bethanie Mattek-Sands later, with a mixed-doubles match to follow the women's singles.
Earlier, Wimbledon champion Petra Kvitova and Tomas Berdych won singles matches to give Czech Republic a 2-1 win over Bulgaria.