MELBOURNE, Jan 24 (Reuters) - Spaniard Rafael Nadal set his sights on the world's top 20 after pushing third seed Lleyton Hewitt to the limit in a pulsating Australian Open fourth-round match on Monday.

Australian Hewitt recovered from two sets to one down to deny the 18-year-old Nadal a place in his first grand slam quarter-final.

"In the fourth set, I had big chances," Nadal told reporters. "I had three times 15-30, and at 4-4 I had 15-30.

"Today I didn't play bad in the important moments, but he played very, very good in the important moments, and he won because of that."

In front of a packed crowd at the Rod Laver Arena, Nadal dominated Hewitt for long periods as his sizzling forehand worked to perfection.

Hewitt snatched the fourth set in a tiebreak and with the Spaniard suffering from leg cramps the home favourite held on to clinch the decider 6-2.

Nadal, who ended 2004 in style by beating world number two Andy Roddick to help Spain defeat the United States in the Davis Cup final, was proud of his performance.

"I am happy because I played a good match and I had a lot of chances for a win," he said.

"I am happy because he is number three in the world and I played the same as him today. If I play at this level, I can do important things this year."

Hewitt has tipped Nadal as a future French Open champion, with the slow clay surface likely to suit the Spaniard even more than hard courts.

Nadal has never played at Roland Garros due to injuries and will not be aiming too high when it comes to the next grand slam of the year.

"My mission for the French Open is just to play the French Open," he said.

Nadal's ranking is sure to rise after reaching the last 16 at Melbourne Park but he is already looking further ahead.

"I want to be in the top 20 and the top 15 is my objective," he said.

NOTE: Rafa told the Mallorcan press that now that his participation in the clay Masters events appears assured, he would like to arrive at Roland Garros as a seeded player. Vamos, Rafael!