Formula One world champion Michael Schumacher sees McLaren as a potential threat to Ferrari's domination this season after David Coulthard's impressive times in recent testing.

"I have been impressed by the step forward carried out by McLaren," the German told Friday's Gazzetta dello Sport newspaper.

"I think it is due above all to the good work done by their tyre supplier. But on the other hand, I have already said that I expect a closer championship."

Coulthard was fastest in testing in Valencia on Thursday and the only driver to lap in under one minute 11 seconds. Schumacher clocked a time of 1:11.528 after running into the gravel trap on a windy afternoon.

Mercedes-powered McLaren were third last season, with Coulthard picking up their sole win in Monaco, and have decided to delay the introduction of their new car until the fourth or fifth race of the year to allow them to make a bigger leap forward.

Ferrari, who won 15 of the 17 races last year, are also expected to delay the introduction of their F2003 leaving Williams, runners-up in 2002, as the only one of the top three teams set to start the season in Australia on March 9 with their new car.

Williams, with Colombian Juan Pablo Montoya and Schumacher's younger brother Ralf, were launching their BMW-powered FW25 at Barcelona's Circuit de Catalunya on Friday.

Both McLaren and Williams use Michelin tyres while Ferrari have a very close relationship with Bridgestone.

Schumacher also backed new technical changes, including the decision to strip out so-called electronic 'driver aids' and the introduction of the HANS head and neck protection system that is now mandatory.

"They are correct decisions for the future of the sport," he said.

"The (HANS) system in itself doesn't create any problems for the driver, in fact it has been shown to be a great benefit in the case of a frontal impact. But it needs to be developed properly so that it becomes comfortable."