By Andrew Benson BBC Sport Online motorsport editor

US motor racing series Cart has performed a U-turn in its attitude towards the rival Indy Racing League.

Cart has been suffering in recent years and had been pursuing a policy of appeasement towards the IRL - but it now appears to have decided to go head-to-head with its rival.

More and more Cart teams were showing an interest in competing in the Indianapolis 500, America's biggest motor race, which has been part of the IRL since 1996.

This had had an effect on many of Cart's policy decisions in recent years - most notably the adoption of IRL's chassis and engine rules for next year.

Penske have switched camps, abandoning Cart for the IRL

But Cart has now reversed many of the policies that had seemed to be leading slowly towards a unification of the two series.

Most strikingly, Cart is expected to schedule races next year in May, a month that is almost entirely taken up with practice and preparations for the Indy 500.

New Cart boss Chris Pook is not expected to schedule a race in 2003 on the same weekend as Indy, which takes place on the last weekend in May.

But Pook has telegraphed intentions to run races on other weekends in the month, according to Autosport magazine.

Cart teams have said that the plans will not stop them entering a satellite outfit in the Indy 500 next year.

On top of that, Cart has reversed its plans to adopt the IRL's chassis and engine rules for 2003.

Cart's hand forced

The original decision came in October last year and would have made it much easier for Cart teams to run at Indy.

Following on from the decision of Cart's most successful team, Penske, to switch to the IRL for this year, it was expected to bring further moves towards unification.

Penske's owner, Roger Penske, believes there is not room for two single-seater racing series in the US.

But since then the IRL has made moves to prevent the two series running to the same rules, forcing Cart's hand.

Cart had already decided to keep its current chassis rules for 2003, and this week it has decided to do the same with its turbo-charged engines.

The IRL uses 3.5-litre normally-aspirated motors - and its success has persuaded Honda and Toyota to switch from Cart for next year.

Cart has solved the consequent engine-supply crisis by persuading Ford-owned Cosworth to supply all its teams with engines next year.

Long-term plans

Pook said: "Our supporters made it abundantly clear that they preferred the turbocharged formula to the normally-aspirated option.

"We are pleased to be able to respond to their concerns with this agreement.

"This is the first of what we expect will be a number of positive moves that Cart will take in the near future regarding our engine programme."

In addition to the attack, Cart will subsidise teams with a combination of direct financial assistance and cost-cutting measures worth $1.5m.

Pook is planning to start talks with teams and car manufacturers in an effort to create a new technical formula for 2005.

"We need to recognise and respect that these major auto manufacturers need time to commit to a programme," he said.

"It's not just a matter of designing and building an engine - there is a corporate approval process that we must respect."