Visiting teams Britain, Argentina, and France all won hard-fought doubles matches to take 2-1 leads in the Davis Cup quarterfinals on Saturday.
Meanwhile, the United States couldn't finish off Croatia in Portland, after Marin Cilic and Ivan Dodig gave the brothers Bob and Mike Bryan only their fifth loss in cup doubles, 6-2, 2-6, 6-2, 6-4, and kept the tie alive into Sunday.
Jamie Murray and Dom Inglot put Britain in position to move its cup defense into the semifinals after beating Serbia's Nenad Zimonjic and Filip Krajinovic 6-1, 6-7 (2), 6-3, 6-4 in Belgrade.
Dusan Lajovic won the second singles suspended overnight when he beat Jamie Ward in straight sets in the morning to level the tie, but Serbia captain Bogdan Obradovic decided to rest Janko Tipsarevic from the doubles and save him for the reverse singles on Sunday.
The veteran Zimonjic was paired for the first time in the cup with Krajinovic, who played with an injured wrist and viral infection but dominated the partnership.
On Sunday, Kyle Edmund has a chance to clinch a tie for the first time when he plays Lajovic.
If Britain win, it could play Argentina, which was on the cusp of an 11th semifinal in 14 years after Juan Martin del Potro and Guido Pella won their first doubles match together.
Del Potro and Pella outlasted Fabio Fognini and Paolo Lorenzi 6-1, 7-6 (4), 3-6, 3-6, 6-4 over nearly four hours in Pesaro, Italy.
Fognini began the day by playing the second singles that never started on Friday because of bad light and weather. He bounced Juan Monaco, playing in his first tie in 2 1/2 years, 6-1, 6-1, 7-5, and was so fresh that Italy put him in the doubles and pulled Marco Cecchinato.
Two hours later, Fognini looked fresh but was let down by Lorenzi.
Del Potro, the 2009 U.S. Open champion, was playing his first tie in nearly four years, and his first Davis Cup doubles, but there was no empathy from Italian fans, whose whistling when he served eventually drove the umpire to warn the fans.
On Sunday, the winners of the opening singles meet, Argentina's Federico Delbonis and Fognini, in what could be the deciding match.
Wimbledon doubles champions Nicolas Mahut and Pierre-Hugues Herbert of France won on their cup debut when they prevailed against hosts Lukas Rosol and Radek Stepanek 6-1, 3-6, 6-3, 4-6, 6-4 in Trinec.
Rosol beat Jo-Wilfried Tsonga in a five-set singles on Friday, but was summoned to replace Adam Pavlasek, who had a back problem. Rosol struggled on serve, and was broken in the opening game of the final set in what turned out to be the decisive break.
Tsonga could still have a say in the first reverse singles on Sunday, when he plays left-handed Jiri Vesely for the first time, with a chance for France to win on Czech soil for the first time in 90 years.
In Portland, Cilic, despite losing a five-set singles on Friday, replaced Marin Draganja in doubles, and the move paid off as Croatia won to cut the Americans' lead to 2-1. Cilic has the first reverse singles on Sunday, against John Isner.