Federer in 4th round

Roger Federer reached the fourth round of the Sony Ericsson Open in Miami, but was made to sweat by Frenchman Florent Serra.

The top seed won 7-6 (7/2) 7-6 (7/3) in one hour 32 minutes to set up a meeting with Tomas Berdych of the Czech Republic.

The Swiss star dropped his serve three times, but converted three of the eight break-point chances he had, including two in the second set, and held his serve when it counted.

Serra was let down by his first serve, making just 49%, but Federer will also look to improve on his mark of 58% in the next round.

"Sure, I still have to tidy up my game a bit, having had one break up in the first and two breaks up in the second; it's normally something that doesn't get away from me," said Federer.

"But I thought he came up with some good stuff, and that made it difficult for me to close it ouT... I don't think I gave it to him. I think he went to get it, which is a big difference."

Berdych, the 16th seed, was a 6-4 7-5 winner over Horacio Zeballos of Argentina.

A single break gave Berdych the first set and two more followed in the second, Zeballos claiming one of his own.

The second-highest seed left in the draw, Robin Soderling made lighter work of his match, needing just 65 minutes to defeat Philipp Petzschner 6-1 6-2.

The number five seed will face Chilean Fernando Gonzalez after the ninth seed eventually saw off Juan Monaco 6-7 (4/7) 6-4 6-2 to record his sixth victory in as many games over the Argentinian.

Elsewhere, seventh seed Marin Cilic edged out Marcos Baghdatis 6-3 6-4.

There was little to choose between the pair, who both dropped just four points on their first serve, but the Croat managed to twice break Baghdatis and the Cypriot did not even enjoy a single break-point chance.

Cilic faces Fernando Verdasco in the fourth round after the number 10 seed struggled to a 3-6 7-6 (7/4) 6-1 win over Jurgen Melzer.

The Spaniard got off to a sluggish start before eventually battling through in just over two hours.

American Mardy Fish, Andy Murray's conqueror, claimed another scalp with a 7-5 6-3 win over 29th seed Feliciano Lopez.

Fish carved out 13 break points, converting just two, but saved the two he faced to claim victory.

He will meet 13th seed Russian Mikhail Youzhny who edged out Stanislas Wawrinka 1-6 7-6 (7/5) 7-5.