NEW YORK - Serena Williams is finally taking care of business - tennis business, that is.

For too long the hard-hitting American seemed to find something else - anything else - to do besides dominating the sport that made her a millionaire before she was legally able to drive. There was acting and designing - anything, it seemed, except playing tennis.

No longer. Williams capped her comeback year Sunday night by pounding out a hard-earned 6-4 7-5 victory over Jelena Jankovic to win the US Open women’s singles and return to the world number one ranking for the first time since August 2003, the longest gap at the top for a woman.

“I feel like I have a new career, like I feel so young and I feel so energized to play every week and to play every tournament,” Williams said. “I feel like there’s just so much that I can do in my career yet, and I’ve never felt like I’ve played my best tennis.”

This was Serena’s first Grand Slam title since the Australian Open in 2007 and her third US Open crown, having won America’s premier tennis event in 1999 and 2002. She now has won nine major titles.

It also was the first year since 2001 that Williams played in all four Grand Slam tournaments.

Jankovic, who had a brief one-week stay atop the rankings, showed she belonged among the elite of women’s tennis with a valiant but futile effort to stem the tide. But the outcome of the rain-delayed title match never seemed in doubt. Whenever Jankovic tried to become a factor, Williams stepped up her game and won every important point.

“I really went out there like it’s just another final of a tournament, and I really tried to play my best tennis,” Jankovic said. “You know, we had great points. It was some entertaining tennis out there, but she was, you know, the better one tonight.”

Right from the beginning Williams unveiled her determination that she was once again would rule the roost in women’s tennis. And Jankovic showed right from the start that she was going to make Williams earn anything and everything she got.

After making Williams work through three deuces to begin the match with a hold, Jankovic took the lead when she broke her opponent at love, grabbing a 2-1 lead. Yet every time she inflicted a little pain on her foe, it was like she had rattled a hornet’s nest.

The American ripped through the next four games before Jankovic finally held. The Serbian right-hander, running down seemingly every ball and making her opponent hit yet another shot, broke Williams again, pulling to 4-5.

And again Williams retaliated by breaking right back to close out the opening set.

Finding the passing lanes with her drives down the line, especially on the backhand side, Jankovic took advantage of a slew of unforced errors from Williams to break from deuce in the seventh game of the second set. Then, when she held at 30, Jankovic was only one game away from leveling the match at a set apiece.

She had disturbed that hornet’s nest again.

Williams, fighting off every challenge by Jankovic, won the next four games to close out the victory, tossing her racquet high in the air in celebration.

“I really wanted to win,” Williams said. “Last time I played Jelena I got up and then I kind of had a lot of match points. She’s a player that you have to win the match. She’s not going to give it to you.

“I don’t even remember match point,” the winner said. “I just remember I won and I was so excited. I just knew that I had to go for it.”

Despite her brief stay atop the rankings, this was Jankovic’s first Grand Slam tournament final appearance.

“I had a great two weeks,” she said. “I really fought hard out there every match, and tonight I really gave everything I had. … Serena was a little bit better on the important points.”