Women's seeds Ana Ivanovic and Jelena Jankovic also advanced but men's fifth seed David Ferrer and number 13 Andy Murray exited the tournament.

Top seed Federer, recuperating from glandular fever and without a title this year, surprisingly offered the world number 65 Monfils seven break-point chances, but never lost his serve.

'I tried to play in an aggressive way,' Federer, who broke Monfils serve in the eighth game of the first set and the third game of the second set, told reporters.

'I couldn't really chip and charge the way I wanted to do because he's improved his second serve. I played well on the big points.' Spaniard Ferrer lost 6-4 7-5 to world number 60 Thomas Johansson of Sweden.

Ferrer, who has lost all three matches he has played against Johansson, reached the Miami semi-finals in 2005 and 2006.

Briton Murray, struggling with his serve throughout, wasted two match points before losing to Mario Ancic of Croatia 6-2 2-6 7-6.

Murray has won titles this year at Doha and Marseille but having just watched Ancic, serving at 4-6, save one match point with a winning forehand volley, Murray double-faulted away his second opportunity to close out the match.

'That was just a bad serve,' Murray said. 'It was the first time on tour that I've lost a match when I've had match points.

So that's pretty disappointing.' American Andy Roddick also struggled to find his form but came through a tough 5-7 6-2 6-4 win over qualifier Viktor Troicki of Serbia.

Stunning crosscourt
With Troicki serving at 4-5 in the final game, Roddick hit a stunning crosscourt forehand on the line in the first point of the game and four points later he broke serve to win the match.

'I was pretty lucky,' sixth seed Roddick said. 'I didn't even see it when I hit it.

'I heard people yell and scream afterwards and I figured that was a good thing. As far as freak show trick shots, that's up there. You don't hit shots like that every day.' Women's world number two Ivanovic breezed past Frenchwoman Emilie Loit 6-1 6-2 but fourth seed Jankovic came back from 5-1 down in the third set and saved five match points in the final tiebreak to beat Sofia Arvidsson of Sweden 6-7 6-2 7-6.

Jankovic, who had 56 winners and an equal number of unforced errors, clinched victory on her second match point when a nervous Arvidsson netted a forehand.

Both players displayed incredible shot-making throughout the two and a half hour match with the final set lasting 67 minutes.

Lindsay Davenport
Earlier in the day, Lindsay Davenport's return to the Sony Ericsson Open for the first time in five years proved successful as she won 6-2 6-1 against Camille Pin of France.

'I would have never thought that five years ago would have been my last time I played here,' Davenport said. 'But I didn't play for a couple of years, got injured, was pregnant. Just a lot of things got in the way. -- REUTERS