Roger Federer says Rafael Nadal not best ... Yet

Roger Federer has warned Rafael Nadal that he must win the US Open to stand any chance of being labelled as the greatest to ever play the game.

Nadal has captured eight grand slam titles and time is on the 24-year-old Spaniard's side as he bids to catch the record total of 16 won by Federer.

But Federer, who has won each of the grand slams at least once, said Nadal would have to complete the full set before he is included in the discussion about who is the best ever,

"Clearly he has a chance because he's young enough," Federer said on Saturday after he cruised into the fourth round of the US Open with a 6-4 6-3 6-3 victory over Paul-Henri Mathieu of France. "Having so many French Open titles to his name, let alone at his age, is an amazing accomplishment.

"Then again, obviously I guess he would need to win the US Open, to put himself there. He's won the Olympics, done some amazing things. So he'll have a shot at it, I'm sure."

Second seed Federer and world number one Nadal could meet in the final in New York and the Swiss maestro reiterated that he has become a better player because of the Spaniard.

Nadal has won five French Opens, two Wimbledons and one Australian Open, but has yet to go beyond the semi-finals at Flushing Meadows.

Federer, who completed the full set of all four grand slams when he captured the French Open in 2009, said he saw some similarities between his quest and Nadal's bid.

"I won the other three grand slams rather quickly, like he did," Federer said. "The only difference so far is that I lost two (French Open) finals before, plus a semi-final, whereas he''s never been in a final here."

During his match on Saturday, Federer had as much trouble from the gusting winds that swept through Flushing Meadows as he did from Mathieu.

But after saving one break point at 4-3 in the first set, he won three straight games and then eased to victory, with 13 aces helping him in his cause.

"I thought I played great today in the wind," Federer said. "Once I was able to save the break point and break him, I think it broke his will, maybe."

Federer then broke twice to win the second set and then in the sixth game of the third and though he fell behind 40-0 when serving for the match at 5-3, he held on to clinch victory in one hour 39 minutes.

The five-times champion, whose winning streak in New York was ended in the final last year by Argentina's Juan Martin Del Potro, will now play either 13th seed Jurgen Melzer of Austria or Juan Carlos Ferrero, the 22nd seed from Spain.

"I came through the juniors with both of those guys," Federer said. "I will have my hands full. Regardless who comes through I know it's going to be a tough match."