Motorsport.com has learned that the 24-year-old Californian who made his Formula 1 debut last season, will join compatriots Ryan Hunter-Reay and Marco Andretti and Colombia’s Carlos Munoz at Andretti Autosport, following the team’s merger with Bryan Herta Autosport.

Rossi therefore effectively replaces BHA’s previous driver, 2014 Indy Lights champion Gabby Chaves. Confirmation of Rossi's deal with Andretti-Herta will be released this afternoon.

Rossi, who has not raced in an American series since winning the 2008 Formula BMW championship, told Motorsport.com last week: "F1 still remains the focus, whatever I end up doing this year. But I need to be racing, I need to stay competitive."

Rossi has always had his sights set on becoming the first American grand prix winner since Mario Andretti in 1978, and in 2015 appeared to make a step toward at least establishing himself on the grid. He finished runner-up in the GP2 points table with three wins and four other podium finishes, driving for the Spanish Racing Engineering squad.

Even more significantly, he made his F1 debut with Manor Racing, and in his five grands prix, he outqualifed teammate Will Stevens three of the four times comparisons could be made, and outraced him four times.

However, Manor elected to go with an all-new lineup in 2016, Pascal Wehrlein and Rio Haryanto, and Manor’s were the last seats to be filled.

Rossi told Motorsport.com that he had been talking to a couple of IndyCar teams – this was confirmed independently – and had also considered opportunities in the World Endurance Championship.

Testing schedule

Motorsport.com can confirm that Rossi will not take part in this week’s open test at Phoenix International Raceway, although he will attend. Instead he will test at Sebring on March 1st, sharing the track with Rahal Letterman Lanigan Racing’s part-time rookie, Indy Lights champion Spencer Pigot. Rossi will then continue testing at Sebring the next day, along with the majority of teams and drivers.

Following the opening round of the 2016 season at St. Petersburg, Rossi will again mix it with his rivals, testing at Barber Motorsports Park on Tuesday 15th March. He will get track time at Phoenix before the race weekend, almost certainly running alone.

Aside from the extra sessions allowed at Indianapolis Motor Speedway in the two weeks before the Indy 500, IndyCar rookies are granted just three extra days of testing compared with their more experienced rivals. However, combined with the series’ 2016 relaxation of rules over in-season testing, Rossi should be able to test at all ovals and all road courses before racing on them.