Andy Roddick set a new serving speed record of 150 mph as he powered the United States to a 2-0 lead over Austria on the opening day of their first-round Davis Cup World Group tie in New York.

The world No 2 dismantled Stefan Koubek 6-4, 6-4, 6-2 to give the Americans a huge advantage after Robby Ginepri had battled back to beat Jurgen Melzer, 6-7, 4-6, 6-4, 6-4, 6-2.

Roddick, the 21-year-old US Open champion, needed only 91 minutes to beat Koubek who was probably unsettled by Roddick's first serve of the match which broke the previous fastest serve, held jointly by himself and Britain's Greg Rusedski at 149 mph.

Despite setting the new mark - which he matched later in the first set - Roddick admitted that he was more concerned about his overall serving performance and the result for himself and the team.

"At the end of the day, the thing that matters is that I didn't get broken. And that's the one thing that I'll take any day," he said.

The 21 year-old Ginepri became the first American rookie to win a Davis Cup tie after falling two sets behind.

A surprise choice by US captain Patrick McEnroe for the singles matches, Ginepri was struggling to justify his selection against the world no 76 before redeeming himself with victory on his first match point.

"I was so happy to get through," Ginepri said.

"I was pretty nervous before but kept telling myself to stay calm. I always felt I could turn things around."

The American looked assured early on, racing to a 5-2 lead and holding a set point a game later on his own serve.

However, once Melzer had exposed Ginepri's brittle temperament to break back and force a tiebreak, the momentum changed drastically. The left-hander took the breaker 8-6 on his fifth set point, before opening up a two-set lead by breaking in the 10th and final game of the second set.

Ginepri restored his confidence with an immediate break of serve in the third set and rarely looked back as Melzer became increasingly frustrated with his unforced errors and some inconsistent line calls.

In Adelaide, doubles specialist Jonas Bjorkman and rookie Joachim Johansson put Sweden close to victory over Davis Cup champions Australia, winning a five-set classic yesterday.

In a spiky contest, Bjorkman and Johansson downed the Australian combination of Todd Woodbridge and Wayne Arthurs 7-6, 6-4, 2-6, 6-7, 7-5 in broiling heat in four hours and 28 minutes.

Their crucial victory gave the Swedish outsiders a 2-1 edge going into today's two reverse singles.

The Czech Republic put last year's losing finalists Spain on the ropes in their Davis Cup World Group first-round tie, winning the doubles match yesterday to take a 2-1 lead.

Jiri Novak and Radek Stepanek dominated the match, never losing serve on their way to a 6-4, 7-6, 6-3 victory over Tommy Robredo and Rafael Nadal.