Serbia took a major step towards reaching the semi-finals by outlasting the host USA in a marathon five-set victory in Saturday's doubles competition of their Davis Cup tie.
Ilija Bozoljac and Nenad Zimonjic shocked the top-ranked doubles team of Bob and Mike Bryan 7-6 (7/5), 7-6 (7/1), 5-7, 4-6, 15-13 to give Serbia a 2-1 lead in their best-of-five tie heading into a pair of Sunday's reverse singles matches.
World No. 1 and reigning Aussie Open champ Novak Djokovic can send Serbia into the semis with a win on Sunday over American Sam Querrey, who is ranked 20th in the world.
The 25-year-old Djokovic has captured two ATP Tour titles in 2013, winning 19 singles matches and losing just two. Earlier this year he claimed his sixth grand slam title by beating Andy Murray in the final of the Australian Open.
Querrey has a 13-7 record this year with no titles.
Djokovic has won five of six careers meetings against Querrey, including a 6-0, 7-6 (8/6) win last month in Indian Wells, California.
Serbia defeated the 32-time titlist Americans 3-2 in Belgrade in an opening-round tie three years ago in their lone previous Davis Cup encounter.
In a match that lasted four hours, 23 minutes Saturday, the Serb duo jumped out to a two set lead before the Bryan brothers battled back.
In the other reverse singles match Sunday, Viktor Troicki will take on American world No. 23 John Isner.
Serbia is captained by Bogdan Obradovic while Jim Courier is advising the host Americans.
The winner of the US and Serbia quarter-final tie will meet either Canada or Italy in September.
Meanwhile, Argentina lead France 2-1 in their Davis Cup World Group quarter-final tie after David Nalbandian and Horacio Zeballos came from behind to win Saturday's doubles.
French duo Julien Benneteau and Michael Llodra took the first set but Nalbandian and Zeballos fought back to clinch the match 3-6, 7-6 (7/3), 7-5, 6-3 to give the hosts the upper hand ahead of Sunday's reverse singles.
The teams were all square after Argentine Juan Monaco had levelled the tie following Jo-Wilfried Tsonga's victory over Carlos Berlocq on Friday.
Monaco is set to face Tsonga in the opening singles on Sunday, with Berlocq up against Gilles Simon.
Argentine captain Martin Jaite said: "Tomorrow the match remains very open. We've got the advantage, we've got to get just one point, while they need two. Both singles will be very competitive. We're leading, let's hope we can win.
"Horacio and David were excellent. It was a lovely day with a really important victory. We've got a real Davis Cup team."
"We wanted to put our teammates in the best possible position for Sunday but we didn't succeed," said Benneteau.