JOLIET, Ill. -- Marcos Ambrose will leave NASCAR at the end of the season and return to his native Australia.
The decision was both personal and based on performance, he said Saturday.
Ambrose, from Tasmania, came to the U.S. in 2006 in pursuit of a NASCAR career. As he climbed the ladder from the Truck Series into Nationwide and finally the elite Sprint Cup Series, he always said he'd one day return to Australia so his children could attend school in their native country.
The decision to return at the end of the 2014 season was made this summer, Ambrose said, and comes amid mounting speculation that he will join Roger Penske as Penske prepares to enter Australia's V8 Supercar Series. Penske acknowledged in July he was "looking at the opportunity" to work with Ambrose in Supercars, and team President Tim Cindric tweeted the team will hold a Monday night teleconference to give an "update for the media" on V8 Supercars.
Ambrose wouldn't discuss his future racing plans on Saturday at Chicagoland Speedway, where Richard Petty Motorsports announced via news release that Ambrose was exiting the No. 9 Ford.
"There has been a lot of conjecture through the years, but I just want to get my kids home to enjoy the Australian lifestyle so they can make a good choice when they grow up," he said. "This is really a racing choice for me and I feel like the time is right for me to stop in the U.S. Personally, I think it is a great time to move back home to Australia with my family."
RPM wanted Ambrose back in the seat of the No. 9 Ford and said team owner Richard Petty left the decision was up to Ambrose. He's been with RPM since 2011 and has two wins and 44 top-10 finishes.
He had a shot to make the Chase for the Sprint Cup championship field at Watkins Glen, but lost a duel with A.J. Allmendinger in the closing laps and settled for second while Allmendinger earned the automatic berth into the Chase.
Ambrose said his decision to return to Australia had already been made, and winning Watkins Glen and earning a spot in the Chase would not have made a difference.
"I feel like my level has plateaued at the Sprint Cup level," Ambrose said. "I haven't kicked off the next level. I've always said that if I felt like I had flattened off my learning curve or my success -- that I was only in the U.S. to win and if I wasn't able to compete like I want to, then I need to look at my situation.
"That has been the case. It has been a tough couple years on the race track for me and the personal situation is clear, and I just think the timing is right to go home."
Petty thanked Ambrose for his dedication to the team and said he understood his decision.
"He came over to the United States with his family and dedicated his time here to giving it the best he had each week," Petty said. "I couldn't ask anything more from Marcos and his commitment on and off of the track to our race team and our partners.
"Away from the track, he's a family person first. That's something I respect and we'll miss Marcos, (wife) Sonja and their children."