Brazil's Marcelo Melo and Bruno Soares upset the top-ranked Mike and Bob Bryan 7-6 (6), 6-7 (7), 6-4, 3-6, 6-3 and kept the United States from clinching the first-round Davis Cup tie on Saturday.
It was only the third time the Bryan brothers dropped a Davis Cup rubber. It was just the second time they lost a five-set match. Their only other five-set defeat was in 1999 at Wimbledon.
The United States has a 2-1 advantage heading into Sunday's reverse singles.
John Isner faces Brazil's Thomaz Bellucci in the opening match. If Bellucci wins to even the score at 2-2, Sam Querrey of the United States and Thiago Alves of Brazil will meet in the deciding match.