Force India's Sergio Perez set the pace from Kimi Raikkonen at a drying Monza after heavy rain had lashed F1's fastest circuit.
Sebastian Vettel and Kimi Raikkonen have stressed Ferrari cannot take their current car advantage for granted heading into the Italian GP.
McLaren have confirmed they have held talks with Sergio Perez about returning to the team for 2019.
Daniel Ricciardo is hoping for a "crazy" Italian GP as he braces for engine penalties that will demote him to the back row of the grid.
Lewis Hamilton will not be present for Thursday's media day at the Italian GP owing to an "unavoidable personal commitment".
Mercedes boss Toto Wolff says he is "very curious" to see if Ferrari will once again posses the faster car at this weekend's Italian GP.