Bjorn Borg confirmed his continued regin as the No. 1 tennis player in the world today, vanquishing John McEnroe, the last pretender to his throne in 1979, 6-7, 6-3, 7-6, in a splendid semifinal match in the $400,000 Colgate Grand Prix Masters Tournament.

Having beaten the 20-year-old lefthander who is considered the man most likely to succeed him eventually, Borg, 23, will go for the $100,000 first prize and his first Masters title Sunday (WDVM-TV-9, 4 p.m.) against a man who never has beaten him in a tournament: Vitas Gerulaitis.

Gerulaitis, who reversed the result of the U.S. Open final and beat McEnroe, 3-6, 7-6, 7-6, in the last round-robin match of the tournament Friday night -- today beat Jimmy Connors for the first time since 1972, 7-5, 6-2.

In an extraordinary display of largess, Connors gave away a set point after Gerulaitis got a bad call while serving at 3-5 in the first set. Connors never got another, as Gerulaitis played steady, served well and took advantage of Conners' increasingly ragged play to beat the game's most notable falling star for the first time in their last 17 meetings.

The final can hardly help but be anticlimactic after the exquisite 2-hour, 41-minute test of nerve and shotmaking that Borg and McEnroe produced today at Madison Square Garden, with the No. 1 ranking for the 1979 season on the line.

Gerulaitis has a career record of 0-14 against Borg, but he cautioned observers not to jump to any conclusions. The flamboyant "Broadway Vitas" is in a buoyant frame of mind after defeating McEnroe and Connors both within 16 hours, and eager to beat Borg for the first time in his hometown.

But on today's form, Borg will be most difficult to overcome. The four-time French Open and Wimbldeon champion is at his best when the pressure is most intense, and he summoned all his reserved of competitiveness and skill in the final set against McEnroe, winning the decisive tie breaker, 7 points to 1.

On Thursday night, Borg beat longtime arch-rival Connors in a match out of their book of memories, delicious in its intensity and drams, 3-6, 6-3, 7-6, 7 points to 4 in the final tie breaker.

Today's match was stylistically quite different from that all-out war from the baseline: a physical chess game pitting McEnroe's penchant for getting to the net behind serves and chips and slices against Borg's incomparable back court game and passing shots. But ultimately it may have reached even giddier heights.

By the end, it too was a lovely little war -- one of quick strikes and modern weapons improvised for the occasion.

Some of the points were exhilarating, the overall standard of the final set sublime. As these two proud and nrveless perfectionists attacked each other point for point and game for game, the outcome became a matter of compelling drama for 15, 432 enthralled onlookers who filled the Garden with applause, cheers and squeals of admiration.

As befits a showdown for No. 1, this match was close all the way. Each player's best shots seemed to inspire a response in turn from the man across the net.

Borg led, 4-2, in the first set, breaking McEnroe's serve from 40-15 in the fifth game with four crackling passing shots, two of them returns of serve, and saved four break points in the next game.

McEnroe broke back to 4-4, after three deuces and two earlier break points, on one of several spectacular points that will be replayed often in the mind.

McEnroe got to the net and made two reflexive stab volleys off Borg hummers from midcourt, then pounced on a backhand down the line and slashed the ball away with a ferocious backhand cross-court angled volley.

Borg survived two set points at 4-5, on an ace and a smash that McEnroe netted from practically on top of the net, but lost the set in a tie breaker, 7 points to 5.

"I felt the first set was mine. Even though I lost it, I felt in the match," Borg said later. This may explain why he was so annoyed with himself for netting a backhand in the sixth game of the second set, enabling McEnroe to excape a 15-40 jam, that he muttered a single four-letter epithet clearly audible to courtside spectators. For the stolid, unlappable Borg, who never displays emotion on court, this was tantamount to a screaming, cursing blue funk.

But Borg held at love, then broke McEnroe from 40-15 with a backhand lob that McEnroe could barely tick with a desperate leap and a backhand down the line that forced a lunging backhand error. The ball did a teasing little dance on the net cord, then fell back as a look of futility spread across McEnroe's chronically sour puss.

Into the third set they went, and Borg broke again in the first game on another all-time point.

McEnroe served, Borg hit a great return, McEnroe saved himself with a lunging low volley that droped short.

Borg dashed in, got to a ball just before it died, and flicked a backhand lob over McEnroe's head to the baseline. McEnroe chased down the ball just before it bounced for the second time and scraped it back with a desperate, improvisational stroke, his back to the net. That was a "get" that defied belief, but Borg was there to tap away a forehand volley.

Borg held for 2-0, but lost his serve in a bad fourth game.That was the last of those. Both players held the rest of the way to the tie breaker, the level of play rising as the pulse quickened.

Into the ultimate tie breaker, and McEnroe pounded his fourth ace down the center line on the first point. It was the only one he got.

Borg forced two errors, then ripped a forehand down-the-line pass for 3-1. McEnroe, finally getting tight, overhit a high forehand volley, and the deluge was on. Borg seized the last point with a backhand cross-court return winner, and walked slowly, calmly, to the net to shake hands: an appropriate final sequence of tableaux for this majestic match.

The tennis in the Gerulaitis-Connors match was forgettable by comparison, but it will be remembered for one point: the set point that Connors gave away.

Lobbing smartly to punish Gerulaitis for crowing the net, Connors broke for 4-3 and held for 5-3. Gerulatists saved one set point with an ace in the next game, but then hit a lob wide to give Connors the advantage.

Gerulaitis served another ace wide to Connors' left-handed forehand, but the ball was called a fault Gerulatis, alreay enraged by several other bad calls, was clearly disgusted. He served his second ball, and Connors just lollipopped it over the net and walked away, conceding the point to the startled Gerulatis, who tapped it back for a winner as the crowd cheered Connors' unexpected show of sportmanship.