John Isner powered the United States to victory over Australia in the Davis Cup World Group tie with a masterful serving performance at Kooyong on Sunday.

The towering Isner served 49 aces in delivering a 6-4, 6-4, 5-7, 7-6 (7/4) victory over Australia's Bernard Tomic in two hours 15 minutes in the fourth rubber to clinch the tie with an unassailable 3-1 lead.

It puts the Americans into the quarter-finals of the men's team competition with a home tie against either Belgium or Croatia and leaves Australia in a play-off to hold on to their World Group status for next year.

"After the last couple of years it's massive for us," American captain Jim Courier said.

"This is a tough match-up on paper and it was a tough match-up in reality when we stepped on the court. So for us into the second round, it's a big deal."

The United States are the most successful nation in Davis Cup, having been crowned champions 32 times.

It is the first time since 1979 that the United States have beaten Australia on grass and their first win in the traditional rivalry on any surface since 1997.

Whirlwind serving

Australia had not lost in Davis Cup at Kooyong, the former home of the Australian Open, since the 1946 Challenge Round when Jack Kramer, Ted Schroeder led the USA to a 5-0 sweep.

It completed a big weekend for Isner, who cruised to a straight-sets win over Sam Groth in Friday's opening singles before trumping Tomic on the Australians' choice of a grass surface.

It was a dominant serving performance by the 2.08-metre tall (6ft 10in) Isner and set the tone from the first point.

Isner served at 76 percent, won 81 percent of his first serve points and broke Tomic's serve twice.

He cranked up a fastest serve of 253 kilometres per hour (157 miles per hour), which is claimed to be the fastest serve ever above challenger level.

"It's breathtaking to watch him serve the way he did. You know Bernie, I think is one of great return cover players in tennis," Courier said.

"I think he gets so many balls back, he's long and for John to serve the amount of aces that he did today and to serve the quality high percentage that he did all day long in a match that he obviously was feeling the pressure.

"It's Davis Cup last day, you're going to feel it. He stepped up big for us. He's done it for us in Davis Cup before and he did again today."

Tomic appeared passive and distracted early in the match and was overheard during a changeover questioning teammate Nick Kyrgios's absence from the tie after pulling out citing an illness.

During a changeover with team captain Lleyton Hewitt, television microphones caught Tomic muttering: "Nick's sitting down in Canberra. Bullshit he's sick."

Tomic was also heard to say "that's twice he's done it", in possible reference to Kyrgios's withdrawal from the tie against the Czech Republic last year.

Isner began confidently, only dropping four points on his service in the first two sets, before Tomic rallied to take the third set 7-5 to fire up the home crowd.

But the American held his nerve to clinch the match after trailing 1-3 in a tiebreaker, before claiming the fourth set with two powerful serves after Tomic had overhit a forehand.

It took world number 11 Isner's record in Davis Cup competition to 11-9 and 2-0 over the 20th-ranked Tomic.

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