Three months short of her 17th birthday, Tracy Austin became the youngest women's champion in the history of U.S. Open tennis tournament today by ending Chris Evert's streak of four straight titles in the event, 6-4, 6-3.

And did the little girl in pigtails feel sorry that she ruined the old married lady's chance for a record fifth straight?

Diplomacy wrestled with candor. Candor won.

"Honestly?" Austin said behind a self-conscious smile. "No," she then said. No sympathy for the fallen queen, a doddering 24. "No, I wanted to win, too. She's won four times, let me have a chance."

Mercilessly precise with her metronomic ground strokes, unshakably poised in front of nearly 20,000 spectators and utterly unawed by the sight of a tennis immortal across the net, Tracy Austin made real a fantasy -- winning her country's most important tournament -- that began to take shape five years ago.

She had seen a young girl just out of high school play in the U.S. Open semifinals on television. "That was when I started to think about tennis more," Austin said today.

The girl she saw on TV was Chris Evert, then 19, who only two months before that had started toward everlasting fame by winning the 1974 Wimbledon championship.

"This is the happiest day of my life," Austin said after so thoroughly dominating Evert that she lost only 12 points in winning the last three games of the first set and the first three of the second set.

They are tennis twins, the kid and the queen, nerveless technicians from the baseline who will bat balls to and fro until the opponent makes a mistake, either mental or physical. Neither Austin nor Evert has a serve that could go forward in a strong breeze, but they cover that inadequacy by making a mistake, oh, once a month.

Today's victory, then, would go to the player with the smallest of advantages and, as she later confessed, Evert went to the stadium court at Flushing Meadow's National Tennis Center hoping that her reputation in alliance with the majesty of the occasion would give her that small advantage.

It did not.

"I had her 30-love on a couple games and lost them," Evert said."When I lost those, I saw she was mentally tough. I doubted that before the match. I thought maybe the title would intimidate her. But she was out there like it was just another tennis match."

Twice in the first set, Evert broke Austin's serve. Each time, Austin immediately broke back. No frightened child, this.

It was 3-3, Evert leading 30-love on her serve, when Austin began a streak of perfection that didn't end until she had won six straight games and effectively claimed the $39,000 first prize.

Evert lost that game on her serve by making three mistakes, the last a wide overhead off an astonishing retrieval. Austin had gone deep to the backhand corner, sprinting after an escaping Evert volley, and helplessly wristed it back into play.

Evert had struck a winning shot, the volley; Austin had somehow got it back into play, and Evert, who has been perfect for so long, was imperfect when she needed to make a simple killing shot.

Austin won the next game from 30-all when Evert weakly netted a forehand return of the second serve and then failed with a high-risk drop shot.

Three more Evert mistakes, on her serve, put Austin in position to close out the first set and she did it with a strong forehand down the line at which Evert could only lunge, the effort wasted on a backhand shot that flew far, too far, over Austin's head.

Mentally tough, Evert said of Austin. A measure of that grit came in the first game of the second set. On her serve, Austin went down, love-40.

"If you win the first set, you tend to let up," Austin said, "I did let up."

But not for long.

She won the next five points. One was illustrative of Austin's boldness today. At 30-40, she sent a backhand not cross-court, as she had done all day, but screaming down the line. The queen was left flatfooted by the kid's daring.

When Evert next plinked over a drop shot off an Austin lob, it seemed a certain winner. But Austin reached the drop shot and put away a forehand deep in the corner to gain the ad on her serve. An Evert error then gave away the game, and it was only a matter of time.

"Tracy just doesn't give any free points," said Evert, of whom the same words have been said a thousand times. "You have to outsteady her and be super, super patient. As it turned out, she was more patient than I was."

And how does Austin feel at becoming the youngest champion ever, two months younger than Maureen Connolly in 1951?

"I didn't think about the 'youngest' part," Austin said. "Just the 'champion' part."

Tough kid.