Alonso expects surprises in Monaco

"In Monaco there are always some surprises, as we saw last year when Williams finished second and third," said the Renault driver, who has yet to appear on the Monaco podium in four attempts.

"There will be some teams here that will be a surprise and will be in front of the top teams. Hopefully it will not happen to us," the 24-year-old Spaniard told reporters.

"Every year it's a different team but Williams, Red Bull, BMW... one of those teams - normally in Monaco they are extremely quick and cause some trouble to you."

Nick Heidfeld, now with BMW Sauber, was second in Monaco last season with Williams, while his then-teammate Mark Webber was third.

Qualifying will be crucial on a tight and twisty street circuit where overtaking is almost impossible and drivers fear that the new three-part knockout format will turn Saturday into a lottery.

"I'm sure that on Saturday afternoon we have a lot of discussions between the drivers," said Alonso.

"We have to be patient, we know that it's impossible for everybody to get a clear lap with 22 cars in three kilometres in one minute.

"The most important part of this weekend is the qualifying, but at the same time it's the most difficult part."

Alonso won his home Spanish Grand Prix this month, an experience he likened to taking the title last year, but winning Monaco would also rank high in his list of great moments as one of a handful of special circuits.

"Monaco, Indianapolis and Barcelona for me," he said. "Circuits with big names, history in Formula One and motor racing and for sure a victory here is great."

The Spaniard's biggest rival before Thursday's practice was Ferrari's Michael Schumacher, the seven-time world champion who can equal Brazilian Ayrton Senna's record of six wins in Monaco this weekend.

McLaren's form, with Colombian Juan Pablo Montoya the fastest race driver in practice and last year's winner Kimi Raikkonen sixth, has forced him to recognise a new challenge.

"It seems that Ferrari and McLaren are both in good shape here and our main competitors will be them probably," he said.

McLaren, championship runners-up last year, have yet to win a race this season, whereas Schumacher has won twice, and Alonso expected Ferrari to be fighting for pole position. Ultimately, the car will make the difference however.

"Monaco is a drivers' circuit, for sure, but it is also a car circuit," he said.

"Michael in the last four or five years has not won here because he didn't have the right car to win. No-one thinks that Michael was not able to win because of his driving style."