MONZA, Italy -- Lewis Hamilton had the fastest time in Friday's second practice session at the Italian Grand Prix, as championship leader Fernando Alonso endured more problems with his Ferrari.

As speculation about his future and a possible switch to Mercedes continues to dominate, Hamilton spearheaded a McLaren one-two with a time of 1 minute, 25.290 seconds, just 0.038 seconds faster than teammate Jenson Button.

Alonso was third, 0.058 seconds behind Hamilton, but struggled with his car in both sessions.

After finishing fourth in the morning session, despite a suspected engine failure six minutes from the end, Alonso had a brake problem halfway through the afternoon outing.

The Spaniard eventually returned to the track, only to encounter another technical problem with his car 25 minutes from the end of the session, as his gearbox failed.

"We hoped to have a better practice, but oh well," Alonso said. "We'll just have to use information from Felipe's car. In these situations you need to trust your teammate and thanks to Felipe we won't miss anything from the laps we weren't able to do. I'm more or less happy with the performance, there's just a few small tweaks we need to do for tomorrow.

"It's not much of a concern. Normally things happen on Friday that don't happen on Saturday or Sunday. Sometimes we push things to the limit on Friday and we experiment, so it's not much of a problem. What's more of a concern is that McLaren looked very strong today so we need to find something extra tomorrow."

Alonso saw his lead over Red Bull's Sebastian Vettel cut to 24 points last weekend after his race was ended following a wild multi-car accident caused by Lotus driver Romain Grosjean not long after the start.

Vettel was 11th in the first practice session and 13th in the afternoon.

"We just need to concentrate on our job," Alonso said. "We've done a good performance up until now, but last weekend you saw how things can quickly change and you can lose advantage.

"But at the moment we're the only ones that can do that. We can not finish in Belgium, not finish here and still be one of the leaders. But if one of the others don't finish then they say bye-bye."

Alonso's teammate, Felipe Massa, was fourth in the afternoon session, with Nico Rosberg of Mercedes completing the top five.

Michael Schumacher was fastest in the first practice, posting a time of 1:25.422. The Mercedes driver was 10th in the afternoon.

Ma Qing Hua became the first Chinese driver to take part in an F1 weekend when he took Narain Karthikeyan's place in the first session. He was slowest of the 24 drivers, nearly six seconds behind Schumacher.