Nico Rosberg of Mercedes sets the pace in Monaco during practice

The German has been on pole position at the last two races

Lewis Hamilton at the Monaco Grand Prix (GETTY IMAGES)

Nico Rosberg is threatening to claim a third successive pole position after twice emerging the quickest man in practice for this weekend's Monaco Grand Prix.

Rosberg is certainly giving Lewis Hamilton plenty of food for thought as the Briton again trailed his Mercedes team-mate around the streets of Monte-Carlo, as in the last two qualifying sessions in Bahrain and Spain.

Rosberg is currently the man to beat over one lap, and that will be the case again on Saturday once Formula One has enjoyed its historic rest day here on Friday.

On both the soft tyre used in the opening 90-minute session, and then the super soft in FP2, Rosberg was quickest, finishing with a lap of one minute 14.759secs around the barrier-lined 3.340km circuit.

Hamilton, only fifth quickest in the morning run, managed second to Rosberg in the afternoon by 0.318secs, with Mercedes suggesting the prospect of another front-row lock-out is on the cards, as in Spain 11 days ago.

Unlike at Barcelona's Circuit de Catalunya where aggressive tyre wear resulted in Rosberg and Hamilton going backwards in the race to wind up sixth and 12th respectively, Monaco should be a different story.

If both are on the front row again, and in whatever order, victory should follow given the difficulties in overtaking.

As Mark Webber conceded yesterday following his win here last year, it is easy enough to "create a train" behind when tyre management is of the essence.

Behind the Mercedes duo were Ferrari pair Fernando Alonso and Felipe Massa, both around half a second off of Rosberg's pace, with Webber sixth quickest in his Red Bull.

The 36-year-old Australian was then followed by Lotus team-mates Kimi Raikkonen, four points behind championship leader Sebastian Vettel going into this race, and Romain Grosjean.

The Frenchman's practice, however, came to an end with almost an hour to run after he smacked a barrier on the exit of Ste Devote at the bottom of the hill, dismantling his front-left wheel.

The marshals, as is customary in Monaco, performed wonders in lifting the car off track and clearing away the debris as cars continued to flash by.

With the circuit clear, the session was red-flagged moments later as kerb damage was detected at turn 13, on entry to the swimming pool complex, that required a four-minute repair.

Both incidents came at a point when the teams were putting the cars through their qualifying-run paces having switched to the quicker of the two Pirelli compounds available this weekend, the super-soft.

McLaren's Jenson Button was eighth on the timesheet, 1.2secs adrift, with Red Bull star Vettel and Force India's Paul Di Resta completing the top 10, the Scot 1.287secs down.

Given the pace of the Mercedes, there may be issues for the likes of Marussia and Caterham come qualifying and the 107% rule as British rookie Max Chilton and Dutch new-boy Giedo van der Garde were both over four seconds back.

PA