Dixon has one more test to prove his worth to Williams

That is the view of Frank Williams, whose team tried out Dixon at France's Le Castellet track last month.

"He could be a very good prospect one day," said Williams, who needs at least one new driver for 2005.

"He's a very sensible guy, very mature head on his shoulders. We were quite impressed by his ability and feedback."

The 23-year-old New Zealander is to have a more extensive test with Williams at Barcelona's Circuit de Catalunya next week.

Dixon keen on F1 move Dixon tests for Williams

That will enable Williams to better assess whether Dixon could be a candidate for his team next year.

Williams knows that he is losing Juan Pablo Montoya to McLaren in 2005, and Ralf Schumacher is also expected to move on, to Toyota.

But Williams, who has a track record of bringing drivers to F1 from US racing, hinted that he was wary of taking a chance on Dixon.

He warned that F1 was significantly more difficult than the Indy Racing League.

"There's such a big jump now between non-F1 cars and F1 cars themselves because of the electronics and everything on board... So that when a new guy comes into F1 now it's a big jump."

Williams speaks from bitter experience.

Jacques Villeneuve and Montoya both transferred from US racing and became competitive in F1.

But Alex Zanardi, Montoya's predecessor with the Ganassi team in the US, was less successful. He joined Williams in 1999 and had his two-year contract terminated after one poor season.

Dixon also races for Ganassi.