Australian Marcos Ambrose’s career in America’s biggest form of motor racing, NASCAR, is on the line.

The dual V8 Supercar champion is leaving the JTG Daugherty team for which he has driven for five years at the end of this season.

There is the possibility, some say 95 per cent chance, of him joining another NASCAR team – the one bearing the name of Richard Petty, although “The King” who won a record 200 major NASCAR races is now 73 and has little involvement in it.

“The King” was synonymous with Dodge cars, but these days Richard Petty Motorsports - owned by business tycoon George N. Gillett Junior, also in his 70s - fields Fords, which Ambrose raced in Australia and for his first three years in America, before Toyotas.

A senior Ford marketing man in American racing, Tim Duerr, has said Ambrose “bleeds Ford blue, and we would love to see him back in a Ford next season”.

“It all depends on him, a sponsor and a team putting something together, but I am optimistic that we will see Marcos back in a Ford next season,” Duerr said.

However, Ambrose says nothing is certain and that he may return to Australia.

While the Stone Brothers Racing team for which he won V8 Supercar titles in 2003 and ’04, and other Australian teams, especially those running Ford Falcons, would welcome him, he would come home without achieving what he has most wanted in America – to win on the famed oval tracks.

But there is unfinished business here too – a Bathurst 1000 victory eluded Ambrose in his five years in V8 Supercars.

However, Ross Stone, Ambrose’s old boss, can’t see the 33-year-old Tasmanian back racing on Australian tracks next year.

“I don't reckon there's any chance,” Stone told Australian Associated Press last night.

“He's got a little bit of unfinished business and I think he's ready to kick on there (in the US) and finish off what he started.”

For four years Ambrose made progress in NASCAR – initially in its pick-up truck series, then the second-tier Nationwide series, in which he won two races, and from mid-2008 in the premier Sprint Cup.

In his first full Cup season last year he was a creditable, midfield 18th, but this year is languishing 27th.

Last month he was set for victory on the Sonoma road course in California but accidentally stalled while trying to save fuel and earned the unfortunate tag “The Blunder from Down Under” – which luckily for him hasn’t stuck.

Ambrose says he’s going to take seven to 10 days to think things over and has “not discounted returning to Australia”.

“When I came to America, I came on bravery and stupidity,” Ambrose told NASCAR daily bulletin SceneDaily.com yesterday.

“I walked away from a five-year manufacturer contract (with Ford) and a three-year team contract and I felt it was for the right reasons.

“And it worked out. I managed to become a NASCAR driver and live a dream.

“This right now, on the face of it, seems crazy - we haven’t got certainty.

“But I feel like it was the right choice and the timing was right.

“Getting to this point was a big enough drama.

“I’m not sure what’s in store for me, but I feel like it was the right decision … I’m ready for a change.

“I’m just sitting back here (in Charlotte, North Carolina).

“I’m going to just pause for a few days and see what shakes out.

“I’m 33, and we’re a young family (he has two daughters with his fellow Tasmanian wife) and we need to look at all options.

“I feel a little stale in the sense that we (him and JTG Daugherty, owned by former basketball champion Brad Daugherty and husband and wife Tad and Jodi Geschickter) weren’t progressing like we needed to.

“I didn’t want to hold the team back.

“There were question marks why I was running so bad, and I just want to help them rebuild this year, get to victory lane and transfer to a new driver.”

The team promptly announced that 2000 NASCAR Cup champion Bobby Labonte will replace Ambrose next year.

“It’s not been an easy decision,” Ambrose said. “It’s not been an easy process to get to this point. JTG are good friends and have all been very loyal to me and tried to do their best. I feel like I have let them down a little bit with this choice.

“It is a personal choice. But I just feel like it’s time for a change.

“I looked deep inside myself to really think about where I want to go and what I want to do.

“I can get an opportunity to stay in NASCAR, which I’d love to do if I could and finish off what I started, or I could go back to Australia and race Australian Supercar Series again, which I’m cool with.”