BELGRADE, Serbia(AP) The Davis Cup run for the United States is over in the first round.

Novak Djokovic withstood 24 aces and outlasted John Isner 7-5, 3-6, 6-3, 6-7(6), 6-4 on Sunday, giving Serbia a clinching 3-1 lead against an American team looking for its 33rd Davis Cup title.

It's the first time since 2005 the Americans were eliminated in the first round, while Serbia advances for the first time in the World Group and next plays bitter Balkan rival Croatia in the quarterfinals.

Djokovic, ranked No. 2, needed 4 hours and 16 minutes to outlast the 20th-ranked Isner, who was making his Davis Cup debut. The U.S. team played without both Andy Roddick and James Blake for the first time since 2000.

Isner fought like crazy, and his serve was unbelievable,'' Djokovic said of the 6-foot-9 American.His serves are coming like from the fourth floor, and I had no idea where they would go.''

Struggling to contain Isner's booming serve, Djokovic smashed his racket in the second set and received a ball violation penalty in the fourth set tiebreaker. The Serb then wasted three match points while leading 5-3 in the fifth set before converting his sixth match point after Isner netted a forehand.

I knew I had to play my best tennis to have a chance against Djokovic,'' Isner said.He returns the serve real well, and my hat is off to him for the victory.''

I double-faulted on two important break points and that's what probably cost me the match,'' Isner said.Four hours is a lot of tennis, and I'm proud how I played.''

Viktor Troicki defeated Isner in the opening singles Friday and Djokovic beat Sam Querrey to give Serbia a 2-0 lead. Isner and Bob Bryan pulled one back for the U.S. by defeating Nenad Zimonjic and Janko Tipsarevic in Saturday's doubles.