Zimonjic and Djokovic needed two tie-breaks to win their doubles

After missing the opening day's singles with flu-like symptoms, he teamed up with Nenad Zimonjic in the doubles to haul Serbia back into the tie.

The pair beat Mikhail Youzhny and Dmitry Tursunov 6-3 7-6 (8-6) 7-6 (7-5) to leave Russia 2-1 up in Moscow.

Elsewhere, holders the USA, Argentina, France and the Czech Republic all secured quarter-final places.

With Janko Tipsarevic withdrawing on the eve of the tie in Moscow through injury, Serbia are now relying on Djokovic playing in the singles on Sunday to give them any chance.

This was a tough match against a difficult team on a surface we don't particularly like and to finish it by Saturday is pretty satisfying US captain Patrick McEnroe

"I had a lot of difficulties in the last few days with a virus infection," said the world number three.

"I tried to recover as much as I could but it takes several days to get back to normal. I felt pretty exhausted but it's getting better.

"A lot of people expect me to play tomorrow and I can't deny it. They are still the favourites but we're not giving up our fight."

In Vienna, Bob and Mike Bryan hammered Austria's Julian Knowle and Jurgen Melzer 6-1 6-4 6-2 to give the USA an unassailable 3-0 lead.

"This was a tough match against a difficult team on a surface we don't particularly like and to finish it by Saturday is pretty satisfying," said US captain Patrick McEnroe, whose side play France next.

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The Czech Republic went through after Tomas Berdych and Radek Stepanek beat Belgium's Kristof Vliegen and Olivier Rochus in an epic encounter, 6-7 (2-7) 7-6 (8-6) 7-5 5-7 6-4, in four hours 21 minutes.

David Nalbandian and Jose Acasuso took Argentina 3-0 up on Great Britain in Buenos Aires, and Arnaud Clement and Michael Llodra beat Romania's Florin Mergea and Horia Tecau 6-3 6-4 6-7 (6-8) 3-6 6-2 to secure their tie for France.

"It made me mad to see it go to a fifth set. They scared me and all the staff," said French captain Guy Forget.

Germany lead South Korea 2-1 in Braunschweig after Philipp Kohlschreiber and Philipp Petzschner beat An Jae-sung and Jun Woong-sun 6-1 6-3 6-3.

And Israel moved 2-1 up on Sweden in Ramat Hasharon as Andy Ram and Jonathan Erlich defeated Simon Aspelin and Robert Linsdtedt 6-3 7-6 (7-3) 7-5.