Lewis Hamilton stayed top at Monza on Saturday morning, as the McLaren man went fastest in the final free practice session for the Italian Grand Prix.
But it was close. The Briton, who was also fastest in free practice two, beat Fernando Alonso to the top spot by just one thousandth of a second as prospects for a close fight for pole continued to grow.
Paul di Resta was an impressive third fastest in the Force India, which made news of his gearbox penalty all the more disappointing ahead of qualifying.
Hamilton signalled McLaren's intentions early on after the traditional early-session lull, going fastest with a 1m25.508s. Within moments that was challenged first by Sergio Perez in the Sauber, and then Lotus's Kimi Raikkonen.
But by the end of his long run on the hard tyres Hamilton had achieved an impressive 1m24.687s - faster than anything recorded yesterday - to establish himself at the top of the times ahead of his team-mate Jenson Button.
Just after halfway through the session though Alonso weighed in with his own hard-tyre effort - a 1m24.632s lap - that put him top in the Ferrari, while not long after that Rosberg was the first of the frontrunners to switch to the mediums. The Mercedes driver could only manage third however.
Rosberg's team-mate Michael Schumacher, who had been fastest in free practice one, was out of the picture by this stage with yet more reliability issues - this time with his KERS, so the five-time Monza winner instead focused on race set-up.
Into the final 10 minutes and most people switched to their low fuel, option tyre runs. Alonso was the first to fire in a time - 1m24.579s - only to see that beaten by 0.001 second by Hamilton.
And that was the way it stayed, ahead of di Resta and Felipe Massa in the second Ferrari. Button was fifth, having failed to get a clear lap towards the end of the session, and Rosberg sixth.
Perez was seventh quickest in the first of the Saubers ahead of Raikkonen, Nico Hulkenberg (emphasising Force India's pace) and Pastor Maldonado in the Williams.
Sebastian Vettel, who has not been a factor for much of the weekend so far, was 11th fastest and the top Red Bull runner. But he ended the session parked down at the second chicane with a technical issue and reporting a 'low battery'.
Pos Driver Car Time Gap Laps
1. Lewis Hamilton McLaren-Mercedes 1m24.578s 18
2. Fernando Alonso Ferrari 1m24.579s + 0.001s 15
3. Paul di Resta Force India-Mercedes 1m24.849s + 0.271s 20
4. Felipe Massa Ferrari 1m24.909s + 0.331s 16
5. Jenson Button McLaren-Mercedes 1m24.994s + 0.416s 17
6. Nico Rosberg Mercedes 1m25.036s + 0.458s 22
7. Sergio Perez Sauber-Ferrari 1m25.160s + 0.582s 23
8. Kimi Raikkonen Lotus-Renault 1m25.255s + 0.677s 19
9. Nico Hulkenberg Force India-Mercedes 1m25.289s + 0.711s 20
10. Pastor Maldonado Williams-Renault 1m25.383s + 0.805s 18
11. Mark Webber Red Bull-Renault 1m25.389s + 0.811s 21
12. Sebastian Vettel Red Bull-Renault 1m25.406s + 0.828s 17
13. Bruno Senna Williams-Renault 1m25.461s + 0.883s 21
14. Michael Schumacher Mercedes 1m25.563s + 0.985s 23
15. Kamui Kobayashi Sauber-Ferrari 1m25.689s + 1.111s 22
16. Daniel Ricciardo Toro Rosso-Ferrari 1m25.706s + 1.128s 16
17. Jerome d'Ambrosio Lotus-Renault 1m25.973s + 1.395s 20
18. Jean-Eric Vergne Toro Rosso-Ferrari 1m26.003s + 1.425s 19
19. Heikki Kovalainen Caterham-Renault 1m26.657s + 2.079s 18
20. Vitaly Petrov Caterham-Renault 1m27.267s + 2.689s 16
21. Charles Pic Marussia-Cosworth 1m27.454s + 2.876s 20
22. Timo Glock Marussia-Cosworth 1m27.728s + 3.150s 19
23. Narain Karthikeyan HRT-Cosworth 1m28.035s + 3.457s 23
24. Pedro de la Rosa HRT-Cosworth 1m28.384s + 3.806s 17
All timing unofficial