In a pulsating match that will undoubtedly be discussed for years to come when bizarre and dramatic tennis classics are relived, Roscoe Tanner defeated Bjorn Borg tonight, 6-2, 4-6, 6-2, 7-6, and ended for this year the Swede's dreams of his first U.S. Open title and a possible Grand Slam.

Tanner, serving and returning serve better than in his excruciating five-set loss to Borg in this year's Wimbledon final, won the decisive fourth set tie breaker, 7 points to 2, after Borg had fought back from 2-5 in the set and escaped two match points as Tanner served at 5-4 -- the first on an easy overhead that Tanner hit into the back wall.

At deuce in that remarkable ninth game, after Tanner had saved a break point with his 11th screaming ace, minute delay as the net broke under the impact of a Tanner fault and had to be replaced.

During that unexpected intermission, Tanner paced nervously while Borg, the stolid Swede who has won four French Open and four consecutive Wimbledon titles but has never won the U.S. Open, sat impassively in his courtside chair.

After a two-minute warmup, Tanner was properly given two serves because of the interruption of play beyond his control. He cracked a big serve down the center that Borg could only float wide on the return, and stood at match point.

On the next point, Tanner missed his first serve, came to the net anyway, but hit a weak volley. Borg lobbed off the backhand, but hit was too shallow: a sitter. Tanner leaped for the putaway, but agonizingly hit his smash 20 feet beyond the court.

Borg escaped another match point moments later by forcing a forehand volley error with a buzzing forehand down the line, then got to break point by gunning a forehand cross-court return winner off another weak second serve.

Then Borg dipped a backhand return to Tanner's feet off yet another short second serve. Tanner scooped a backhand half-volley, and Borg blasted a forehand cross-court passing shot beyond his helpless lunge.

For the next three games, the 15,432 enthralled spectators at the National Tennis Center on a muggy night when a hurrican downpour was forecast but only a few sprinkles fell were on their feet repeatedly.

Hours before, in the oppressive heat of the afternoon, defending champion Jimmy Connors had strutted into the semifinals with practically no resistance from Pat DuPre, who was stiff and wooden following a grueling five-set victory over Harold Solomon less than 24 hours earlier.

Connors won, 6-2, 6-1, 6-1, in 1 hour 24 minutes. That match offered absolutely nothing memorable. Tanner vs. Borg, by contrast, was unforgettable -- remarkable for the peculiar conditions in which it was played, the air of impending doom for Borg's aspirations that built as Tanner exploded his serves like firecrackers, the chilling nerve of Borg's gutsy comeback, and Tanner's relief when he finally ended the great Swede's current winning streak at 31 matches.

A man with a big serve -- and Tanner's is the quickest, most deceptive, and most electrifying in Tennis -- has a great advantage in a tie breaker.

Tanner only got 49 percent of his first serves in court in the match, and only three of five in the tie breaker, but he won all five of those points.

Borg had blasted a good serve at 2-4 down in the tie breaker, but Tanner drilled a marvelous return that rocked the Swede back at the baseline and then nailed a forehand passing shot to reach 5-2, with two serves to come.

He missed the first, but came to net as he had all night behind his second serve and coaxed his second volley into an open court after Borg chased down the first.

Now it was match point for the third time -- 15 minutes and a seeming eternity of drama after the first -- and this time Tanner did not miss his first serve. He zinged one to Borg's backhand, and the lunging return was wide.

It was 12 minutes after 10, and Borg's hopes of going to Australia the week after Christmas to nail down the French-Wimbledon-U.S. Australian Grand Slam had evaporated.

"Anytime you play the No. 1 player in the No. 1 match in the world, it makes you realize you can play in that category," Tanner said.

Tanner came out like a man who knew he could do it, serving devastatingly in the first 1 1/2 sets even though he had one break point against him in the fifth game. He lost only seven points in his first seven service games, and broke Borg in the second and eighth games of the first set.

Tanner was pressuring Borg relentlessly, steaming to the net behind returns -- chipped or pounded -- of every second serve. He threatened to blow Borg away, but from 2-3, 15-40 in the second set Borg ran seven straight points -- brushing aside two break points and breaking Tanner for the first time at love. Tanner contributed by missing an indecisive overhead and blowing an easy volley.

After that, Tanner's serving lapsed somewhat, and Borg seemed to get a foothold in the match. But Borg's fortunes changed suddenly again when he lost his serve from 30-30 in the fourth game of the third set, netting a backhand off a deep return of a good serve and a backhand volley off a challenging forehand by Tanner.

Tanner broke again in the eighth game of the third set, and saved four break points in the first game of the fourth.

Tanner was serving mightily again. In the third and fifth games, he delivered seven straight serves that Borg could not return even though he was standing 12 feet behind the baseline to receive. The last three, sealing the fifth game at love, were clean aces.

Borg seemed hopelessly out of it when he lost his serve at 15 in the next game and Tanner held for 5-3.

But then came that wild ninth game, a double fault to 30-30, a winning lob by Borg to get to 30-40, the collapse of the net and Tanner's nightmare overhead.

Some of the points were gripping. Borg's courage was indisputable. But Tanner refused to unravel, and in the tie breaker his explosive serve and the artificial light worked in his favor. "I thought, anything can happen in a tie breaker," Borg said later . . . but this time, unlike Wimbledon, it happened for Tanner.