Italian GP: Nico Rosberg leads Mercedes one-two in first practice

Rosberg posted a lap of 1m22.959s around Monza on Pirelli's soft compound tyre, finishing 0.203 seconds ahead of reigning champion and current points leader Lewis Hamilton.

The duo had traded fastest laps earlier in the session when running the rule over the super-soft compound tyre that initially appeared to be more robust at this track than was the case at Spa Francorchamps in last week's Belgian GP.

Rosberg and Hamilton were again comfortably ahead of their rivals, led by Ferrari's Kimi Raikkonen, who finished 1.088s down, with his team-mate Sebastian Vettel a further quarter of a second off the pace in fourth. Both set their times on soft tyres.

It was a busy session for both Rosberg and Hamilton, finishing joint first and third on the lap completion charts, posting 37 and 36 laps respectively, with Valtteri Bottas in his Williams also out in front with 37 laps.

Ferrari's Raikkonen and Vettel managed 16 and 17 laps respectively as the team limited mileage on the new power unit it has introduced this weekend, spending the final three development tokens of its allocation in doing so, while carrying out checks.

Force India's Sergio Perez was a strong fifth on super-soft tyres, as the team continued its top-five form from Spa last weekend.

His team-mate Nico Hulkenberg gave way to reserve Alfonso Celis Jr, who claimed 12th place, 2.408s behind Rosberg, and three quarters of a second behind Perez.

With Haas also sporting the new Ferrari updated power unit, Romain Grosjean and Esteban Gutierrez were sixth and ninth, three tenths of a second apart, with the duo also on super-softs like Perez.

Bottas and Red Bull's Max Verstappen split the Haas pair, the latter two seconds down, with team-mate Daniel Ricciardo rounding off the top 10, 0.138s behind his teenage team-mate, with all three running soft compound rubber.

Jenson Button and Fernando Alonso finished either side of Celis, although the latter ended the session by crawling back into the pits with a gearbox problem.

Felipe Massa, who announced his retirement from F1 on Thursday, suffered a boost issue with his Williams-Mercedes on his installation lap. That confined him to the garage for the majority of the opening 45 minutes before he emerged to finish 14th quickest, nearly three seconds behind Rosberg.

As part of the ongoing assessment of the halo, Button, Verstappen and Perez all ran. Button was the only one to keep it on for a second lap.

Pirelli's new prototype tyre it is hoping to introduce for the Malaysian GP at the start of October was also given extensive running by a number of drivers as part of its ongoing evaluation.

PRACTICE ONE TIMES: