Ferrari and McLaren on Thursday made it clear they intended to make Sunday's Monaco Grand Prix their private affair.
Ferrari clocked the fastest time in the first practice session with world champion Kimi Raikkonen, while Lewis Hamilton put the McLaren in front in the afternoon session.
In the morning Hamilton was second with his teammate Heikki Kovalainen third, ahead of the Ferrari of Felipe Massa.
The second practice saw Raikkonen third, behind the Williams-Toyota of Nico Rosberg, while Massa came in fourth in front of Kovalainen.
Among the other contenders for Sunday's race, Robert Kubica was sixth in both sessions while two-time world champion Fernando Alonso, who has won the last two Grand Prix here, was seventh in the morning and the afternoon.
Because of the particular nature of the Monaco city track, starting positions will be pivotal for Sunday's race, due to the difficulty in passing.
Speaking at a pre-race press conference, Massa predicted that Sunday ''is again going to be a duel between Ferrari and McLaren''.
He also stressed the importance the driver will make in the race.
''This race is always a real toss-up. Here you have to be really careful on every curve because the car counts but so does the driver,'' Massa observed.
Raikkonen agreed and said ''one of the things I like about this circuit is that, in a sport where the technical side has a very big influence on the final result of a race, here a driver's ability has a greater influence on the outcome''.
Looking ahead to Sunday, Raikkonen, who won here in 2005 with a McLaren, said ''there is nothing quite like the Monaco Grand Prix. To race in the Principality is really different from everywhere else. It's more than just a race, it's a legend among all the races,''
Ferrari has not won at Monaco since Michael Schumacher lifted the trophy in 2001.
Ferrari has won the last four races, after Hamilton took the season opener in Australia, and currently holds a strong lead in the constructors' championship, while Raikkonen is seven points clear on top of the drivers' standings, with Massa second, level with Hamilton
Sunday's race will be a a special one for Frank Williams for it will be his 600th Grand Prix since entering Formula 1 in 1969.
In his career, Williams has seen his team win 113 races, seven driver's titles and nine constructors' championships.
''As most of the people who know me know, reaching 600 Grand Prix doesn't mean a lot to me. In 40 years of racing there have been some brilliant moments but also some sad ones. But for the most part this has been a very pleasing experience,'' Williams said.
The Monaco Grand Prix will also be a special one for Italian driver Giancarlo Fisichella: the 200th Formula 1 race of his career.
''This will be a special race for me. First of all because I love Monaco. It has always been one of my favourite circuits and it is going to be my 200th Grand Prix. I am looking forward to it,'' Fisichella said ahead of the practice sessions.
''Of course, it would also be nice to score some points, but that's going to be very difficult,'' the Force India driver added.
Fisichella made his Grand Prix debut in 1996 driving for Minardi and since then has driven for Jordan, Benetton, Sauber and Renault.
In his career he has won three races, collected 18 podium finishes and totalled 267 points.
