Williams want to retain Ralf Schumacher beyond this year but the price must be right.

Team boss Frank Williams told reporters that, with Colombian Juan Pablo Montoya leaving to join Formula One rivals McLaren in 2005, continuity was important.

While Ralf says money is not the problem, Williams said the decision did come down to cash and the team were 'playing hardball' in negotiations.

"We have agreed to park the problem of money for quite some time and review it mid-season onwards," he said at the team's factory on Thursday.

Ralf, younger brother of Ferrari's six times champion Michael, has been linked to big-budget Toyota in the media.

Williams said there was no rush to fill Montoya's job but confirmed that his team had talked to Rubens Barrichello before the Brazilian extended his contract with champions Ferrari to the end of 2006.

"We'll look at everybody. We've got a list of people that we're looking at," he added.

Briton Jenson Button, who started his career at Williams as a 20-year-old in 2000, could be one of them although he is contracted to BAR until the end of next year and Williams would not comment on the possibility.

"He's a great driver. He's got it coming but in a nice way," said Williams.

WEBBER IMPRESSES

Jaguar's Australian Mark Webber has also been linked to Williams, whose first champion was Australian Alan Jones in 1980, and the team were impressed by the 27-year-old last year.

"We've always thought he was very good, a bit like Nigel (Mansell) in a way, a great charger," said Williams.

"He has to be very highly rated," added technical director Patrick Head.

"If Mark Webber is actually three quarters of a second faster than Antonio Pizzonia then he must be pretty damn good as Antonio seems to be as fast as either of our two race drivers."

Brazilian Pizzonia has returned to his old job as Williams test driver after underperforming against Webber at Jaguar last year and losing that job.

"He's a funny guy," mused Williams. "There's no doubt that he is very quick.

"Nothing's impossible," he added when asked whether Pizzonia might have a chance of a race seat in 2005. "But one worries about what happened to him last year and in his Formula 3000 season before that."

Williams recently tested Nelson Piquet junior and Nico Rosberg, both sons of former champions, and the team boss said both had a Formula One future but were not ready yet.