Federer has won three titles this year

The Swiss player was a break down in the third set before coming back to see off Nikolay Davydenko 6-2 3-6 7-5.

The Wimbledon and Australian Open champion was kept on court for nearly two hours before beating the Russian.

Federer, who has now won 12 matches in a row, admitted he had been close to going out.

"I was very concerned. I was not feeling well today," said the Swiss player.

"There are incredible winds here so it's difficult to play. It was a tough one, I didn't think I was going to turn it around."

There were no such worries for three-time defending champion Andre Agassi, who beat Argentina's Mariano Zabaleta 6-0 7-6 (7-1).

The 33-year-old American hit five aces and only 14 unforced errors to win in 85 minutes.

US Open champion Andy Roddick overpowered Karol Beck of Slovakia 6-2 6-4.

Roddick served 14 aces, including four in succession to take one game without his opponent getting a racquet on the ball.

I'm not satisfied with my performance - this is a match I should have won Marat Safin

The American second seed will now face veteran Swede Jonas Bjorkman, who beat Taylor Dent 7-6 (7-4) 6-2.

Fifth seed Carlos Moya had to work hard before finally seeing off fellow Spaniard David Sanchez 4-6 6-4 6-4.

Former US Open winner Marat Safin was beaten 7-6 (9/7) 6-7 (4/7) 6-4 by Vince Spadea of the US.

Spadea fired eight aces and 41 winners and made less unforced errors and also handled the blustery conditions and key points better than Safin.

With eighth seed David Nalbandian of Argentina withdrawing from the $6.5m hardcourt event, 36th-ranked Spadea now faces Czech Radek Stepanek for a fourth-round berth.

Another seed to go was eleventh-ranked Mark Philippoussis, who went down 6-4 6-2 to Jan Hernych of the Czech Republic.

Thailand's ninth-seeded Paradorn Srichaphan, who could face Spadea in the fourth round, advanced by defeating Spanish qualifier Ricardo Mello 6-1 1-6 6-3.

He fired down seven aces and 22 winners to dispatch Mello in 91 minutes.

Australian 19-year-old wild card Todd Reid rallied to oust 15th-seeded Dutchman Martin Verkerk 4-6 6-4 7-5.

Reid, who reached the Adelaide and Sydney quarter-finals in January, now meets Argentina's Agustin Calleri, who eliminated Germany's Lars Burgsmuller 6-3 7-5.