With Bridgestone due to withdraw from the sport at the end of the season, F1 has yet to decide on a replacement tyre supplier, though Williams' Sam Michael claims the choice is narrowing.

While some, including Pitpass, have expressed concern at the safety implications of leaving it this late in finding a new supplier, the teams appear to be focussing on costs.

In reality, the new supplier should be collecting data at this very moment, what with work on the 2011 cars to begin any time now and their first running in just over eight months. Even though Michelin only left the sport at the end of 2006, the sport has changed dramatically since then, and with the possibility of the reintroduction of KERS next season, will change again.

"The conversations really, at this point, are between Michelin and Avon," said Michael following a meeting of the teams' alliance (FOTA) yesterday. "Avon's a lot cheaper than Michelin but it's a less proven product although they've done plenty of highly competitive tyres.

"They are a bigger unknown than Michelin because Michelin did it very recently," he told Reuters. "But there is a significant difference in cost and you are probably talking over three times the difference in cost to the teams. So that's what's being debated at the moment."

The Australian dismissed claims by Ferrari's Stefano Domenicali that a decision could be made by the time the F1 circus pitches up tent in Barcelona next week.

"I think the discussion in FOTA is just acknowledgement that you've got to take into account a lot of different factors," said the Australian, "it's not a straight financial decision and it's not a straight technical decision. All this needs to be discussed with Bernie as he's traditionally looked after tyre supply."

Only two weeks ago, Michael's colleague at Williams, Adam Parr, the Grove outfit's CEO, revealed that FOTA has charged Bernie Ecclestone with identifying and securing a new supplier, admitting that the teams were not in favour of Michelin's intention to increase the wheel diameter from 13 inches to 18 inches. Such a change would see larger wheels with lower profile tyres which would change the handling and suspension characteristics of the cars dramatically. It's a move not popular with teams who would be forced to redesign their suspension layouts significantly.

Ecclestone is said to be in favour of Avon who would supply a (cheaper) non-branded tyre which would also conform with the current wheel and tyre diameters.