After taking both opening singles on Friday, the Americans had looked poised to make it a clean sweep, sending out the Bryans to face the underdog Brazilians on the lightning quick Jacksonville, Florida hardcourts.
The Bryans entered the match with a sparkling 20-2 record together in Davis Cup competition, but could not put away the feisty Brazilian duo falling 7-6 6-7 6-4 3-6 6-3 in three hours and 29 minutes.
It marked the first Davis Cup loss for the 13 time Grand Slam winners since 2008.
The United States will now need a victory from John Isner or Sam Querrey in Sunday's reverse singles if they are to avoid the upset to Brazil, who are back playing in the world group for the first time in nine years.
Needing a win to extend the tie, Melo and Soares, who had lost only once in five ties, came out and took the opening set in a tie-break 8-6 but Bryans answered right back taking the second also in a tie-break 9-7.
The seesaw rubber continued with the Brazilians recording their first break in the third to grab a 2-1 lead while the American Australian Open champions finally recorded their first break in the fourth set to send the match to a winner-take-all fifth.
- Sports & Recreation