Russia beat Serbia in the Davis Cup when an unwell Novak Djokovic retired from his match against Nikolay Davydenko, handing the home team an unassailable 3-1 lead in their first-round tie.

The Australian Open champion had won the first two sets and was 3-0 up in the third despite being way below his best and often struggling for breath after suffering from flu symptoms in the last few days.

However, Davydenko staged a miraculous recovery to win the third set 6-4, after which the Serbian decided to quit.

"I stopped because I didn't want to risk my health," Djokovic said. "I didn't go to hospital after all but still, I was feeling very dizzy. I was losing a lot of energy. It's not easy to play when you have a virus infection."

Djokovic was taken to a local hospital suffering from exhaustion.

The home team had led 2-0 after sweeping both singles matches on Friday but Djokovic kept alive Serbia's hopes when he teamed up with Nenad Zimonjic to win Saturday's doubles.

With Serbia number two Janko Tipsarevic also sidelined by a stomach bug and ankle injury, the visitors gambled on the unfit Djokovic to challenge the Russian number one.

The world number three, cheered on by a small but vocal Serbian contingent at Moscow's Luzhniki arena, broke Davydenko in the 12th game to take the first set 6-4.

After losing his serve in the opening game of the second set, the 20-year-old Serb broke right back, then repeated the trick two games later to build a 4-1 lead. Djokovic then saved four break points in the ninth to clinch the second set 6-3.

The writing seemed to be on the wall for Davydenko when he fell behind 3-0 at the start of the third set. But the Russian staged a remarkable comeback, reeling off four consecutive games to win the third set only to see Djokovic walking off the court.

"I was completely shocked to see him walking out," Davydenko said. "He played well for more than two hours as I was making a lot of mistakes," added the world number four, who committed 60 unforced errors and only converted four of his 18 break-point chances in the two hour 41 minute match.

"I knew he wanted to win in three sets to save his energy. I had no choice but to keep fighting."

Serbia's Davis Cup debutant Viktor Troicki, ranked 114th, beat substitute Dmitry Tursunov 7-6 4-6 6-3 in the dead last rubber to make the final score 3-2 as the Russians extended their unbeaten home streak to 15 ties. They last lost at home in the 1995 final against the United States.

- - - - - -

Doubles specialist Jonas Bjorkman beat Israel's Harel Levy in four sets to give Sweden a 3-2 win in their first-round tie.

The 35-year-old Swede came back from losing the first set 0-6 to win the next three 6-4 6-3 7-6 in the final reverse singles.

Sweden went into Sunday's reverse singles needing to win both matches. Thomas Johansson started the day by beating Israel's Dudi Sela 7-6 6-1 7-5. Sweden will meet Argentina in the quarter-finals in April.

- - - - - - -

Philipp Kohlschreiber held on to beat South Korea's Lee Hyung-taik 6-0 4-6 6-1 7-6 and send Germany through to the last eight of the Davis Cup with a 3-1 winning lead.

Kohlschreiber was so dominant in the first set on the indoor clay court in Braunschweig that a German victory looked a mere formality but a moment of carelessness let Lee back in and the match turned into a real scrap.

Lee, South Korea's most experienced Davis Cup player, edged into a 3-2 lead with a break in the second set after taking advantage of a limp Kohlschreiber forehand to the net.

The German number one hit back to take the third in a similar style to the first but Lee saved four breakpoints at the start of the fourth set and looked the stronger player for much of it.

Kohlschreiber, who needed treatment on a sore calf, saved his best tennis for the tiebreak, taking it 7-1 to give Germany the vital third point.

Germany, beaten semi-finalists last year, will play Spain in the quarter-finals.

- - - - - -

Doubles specialist Bob Bryan put the seal on a crushing 4-1 victory over Austria to set holders United States off to an assured start in their 2008 Davis Cup defence.

After watching his twin brother and doubles partner Mike limp off after one set against Austrian number one Stefan Koubek with a left hamstring injury, Bob Bryan completed victory with a 6-0 3-6 7-6 win over Werner Eschauer.

The left-hander seemed on course for a far easier day after cruising through the first set in 25 minutes but Eschauer found his confidence and took the second with a series of well angled ground strokes and the odd inspired drop shot.

The third set went with serve until the 33-year-old Austrian, playing only his second Davis Cup singles, tightened up badly in the 11th game on his serve and three unforced errors plus a double fault appeared to have let Bryan in for victory.

Eschauer battled back superbly to rescue two match points and a miscued top-spinner sent the encounter into a tiebreak but Bryan's extra nous and heavier weight of shot eventually told.

Bob Bryan has now won three of his five Davis Cup singles.

The U.S. had made sure of an April quarter-final date against France on Saturday when the Bryan brothers, ranked world number one doubles pair, added victory to opening day successes for Andy Roddick and James Blake.

- - - - - -

Michael Llodra and Arnaud Clement won their reverse singles against Romania to give France a 5-0 whitewash in their first-round tie. The former champions will now play holders the United States away in the quarter-finals in April.

"We will not be the favourites (against the U.S.) and therefore we will have the advantage of playing without pressure," said Australian Open runner-up Jo-Wilfried Tsonga. "I know that the Americans will fear us. Richard (Gasquet) has already beaten Roddick and Blake, and along his side, we defeated the Bryan brothers earlier this year.

"They know we have two top twenty players and a top doubles team and that we can play very high quality tennis."

Clement and Llodra had already teamed up in the doubles to clinch the winning third point for France on Saturday, after Tsonga and world number seven Richard Gasquet had won their singles on Friday.

On Sunday, Llodra beat the experienced Andrei Pavel 7-6 7-6 before Clement beat Horia Tecau 7-6 2-6 6-4.

------

Tommy Robredo and Nicolas Almagro won both reverse singles rubbers to give Spain a 5-0 clean sweep against Peru. The victory propelled the 2004 champions to a quarter-final showdown with Germany in April.

After sealing the tie on Saturday in the doubles, Spain's Robredo beat Peru's Mauricio Echazu 6-4 6-1 before Almagro sealed the sweep with a 6-2 6-3 victory over Ivan Miranda.

Echazu was a last-minute substitute for Matias Silva, who had to withdraw with a stomach problem. Silva himself had been a replacement for Luis Horna, who withdrew with an arm injury.

------

Belgium restored some pride by winning Sunday's two dead rubbers in their Davis Cup tie with the Czech Republic, but the Czech's will meet Russia after their 3-2 win.

Tomas Berdych and Radek Stepanek won their singles matches and then teamed up to win in doubles.

Steve Darcis and Ruben Bemelmans were Belgium's winners in the last two matches with wins over Lukas Dlouhy and Pavel Vizner respectively as Berdych and Stepanek were rested.

Reuters