On the final point of the match, Roddick hit a 152 mph serve - bettering his previous world record of 150mph.
You know, the other night when I was cranking them (serves) out there, and they were coming up large, I felt like I had it in me," Roddick said. "For most of the day I didn't get a chance because my off-speed stuff was a lot more effective than my big serves. But then I felt I'd take a crack at it the last game."
Astonishingly, Bjorkman returned the serve but later in the rally netted a backhand to give the United States an unassailable 3-1 lead in the best-of-five match tie.
To close the tie in the best possible way, Mardy Fish outlasted Thomas Johansson, a last minute substitute for Thomas Enqvist in the meaningless fifth match, 3-6, 6-1, 6-4.
In the final set against Roddick, Bjorkman - who won his opening singles against Fish and played doubles on Saturday - ran out of steam and ran out of answers against a flawless Roddick.
Roddick won 16 of the last 18 points, making Bjorkman look like nothing more than a puppet on a string.
"I felt great out there in the third set," Roddick said. "I wasn't even thinking. It was just kind of like my instincts took over.
"That's as clean as I've felt on the tennis court in a long time - and maybe ever."
Roddick, who has quickly become the leading force of the US Davis Cup efforts, now has an impressive 12-3 win-loss record in eight Davis Cup ties played.
He has now been asked to clinch a Davis Cup tie for the US four times and has come through every time.
This victory, however, was particularly sweet for Roddick, in that he did it in front of friends and relatives in what could be described as his own backyard since his Boca Raton home is only 15 minutes down the road from Delray Beach.
"It's even better when I'm playing for my friends and for my country as well," Roddick said. "It's a lot deeper than just a regular tournament."
The first set was a see-saw battle as both players exchanged service breaks in the opening two games and then again later in the set before heading into the tiebreaker.
The tiebreaker belonged to Roddick from the outset as he raced to a 5-1 lead and then won the set on his second set point when Bjorkman netted a backhand volley.
In the second set, Bjorkman saved one set point on his own serve at 30-40 in the ninth game, but could hang on no longer.
Even so, Roddick needed three set points in the 10th game before Bjorkman netted a forehand to put the US ahead by two sets.
The US will take on Belarus in the semi-finals on home turf in September.
"It will be either this (surface)or maybe clay - that's a possibility as well," said US captain Patrick McEnroe, making note of the slow hard courts here. "The bottom line is if the guys feel strongly about a particular surface, that's probably what I'm going to go with because they're the guys that are out there playing."
France and Spain will play in the other semi-final.
The United States, whose 31 titles are the most in Davis Cup history, are looking for their first Davis Cup title since they beat Russia in the final in 1995.
Their last appearance in the final was in 1997, when Sweden swept the Americans 5-0 in Goteborg.
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