Reuters/Monaco

To further fuel widespread expectations of a fourth successive pole position for the Silver Arrows, teammate and 2008 world champion Lewis Hamilton lapped second fastest in the afternoon.

Rosberg, who has been at home on the twisty streets ever since he was a boy growing up in the principality, clocked a best time of one minute 16.195 seconds before lunch and then 1:14.759 in the second session.

That later lap, set early in the session, compared to last year’s fastest time in qualifying by Mercedes’ Michael Schumacher of 1:14.301. Hamilton was 0.318 off Rosberg’s pace, with drivers using Pirelli’s softest tyre compounds.

While Rosberg will be chasing his third successive pole position in tomorrow’s qualifying, hat-trick chasing Spaniard Fernando Alonso was second and third fastest respectively for Ferrari.

Alonso, winner of his home race in Spain this month, is hoping to become Ferrari’s first Monaco winner since 2001 and the first Formula One driver to triumph in the glamour race with three separate teams.

Teammate Felipe Massa was fourth on a gloriously sunny afternoon with the Mediterranean serving as a sparkling backdrop to the action.

Frenchman Romain Grosjean was third fastest for Lotus in the morning, as he limbered up for his closest thing to a home race in the continuing absence of a French Grand Prix, but then crashed into the barriers at Sainte Devote after lunch.

On a historic course that threads its way up the hill and into Casino square before dipping and winding down to the darkness of the tunnel and blasting past the moored yachts on the quayside, Venezuelan Pastor Maldonado provided the morning’s surprise.

The Williams driver was sixth fastest, although he faded back in the afternoon, on one of the most treacherous and unforgiving circuits on the calendar.

Williams have not scored a point yet this season, a run of six races in a row including last year’s finale, and are in danger of chalking up their worst ever start to a championship this weekend.

Maldonado has form in Monaco, however, winning junior series races there on his way to Formula One and loving the challenge of keeping out of the barriers.

Red Bull’s triple world champion Sebastian Vettel, who has a four-point lead in the standings over Lotus’s Kimi Raikkonen, was only 10th and ninth quickest with Australian teammate Mark Webber - last year’s winner - seventh and fifth.

McLaren’s Jenson Button was eighth in both sessions, with Mexican teammate Sergio Perez ninth and 12th, ahead of what could be another difficult weekend for a team struggling to catch up after starting the year well off the pace.