Alexander Rossi replaces Max Chilton at Marussia for Belgian GP

The British team said Rossi, who joined Marussia last month as a reserve driver, would substitute for Chilton "while contractual issues are resolved".

"Although it was not our intention to offer Alexander the possibility to race this season, in light of the circumstances we are pleased to be providing him with the opportunity to make his grand prix debut at this weekend's Belgian Grand Prix in Spa-Francorchamps," said team boss John Booth.

"Naturally we hope to resume normal service with respect to our established race driver line-up as soon as possible, but for now we wish Alexander well for the weekend ahead and we look forward to seeing him in action."

Marussia has declined to specify exactly what the contractual issues are, but they are likely to relate to the non-payment of promised funding from Chilton's backers that secure him the drive.

Rossi joined Marussia from Caterham, where he was a reserve driver and sometime Friday tester before new owners took over the team earlier this year.

The 22-year-old will be the first American to race in F1 since Scott Speed's final appearance for Toro Rosso in the 2007 European Grand Prix.

"It goes without saying that I am thrilled to be given the opportunity to race in Formula 1 for the first time and I cannot thank the Marussia F1 team for the faith they are demonstrating in me," said Rossi.

"It's a very big moment for me and there's a lot to prepare in a short space of time, but on the other hand I have felt ready for this for quite a while now. It is also exciting to be given this opportunity at such a fantastic and historical circuit as Spa-Francorchamps.

"I can't wait to drive the MR03 from tomorrow and I hope to reward the team with a solid race weekend."

The Marussia driver swap is the second change to the F1 line-up for Spa, with the team's arch-rival Caterham having already replaced Kamui Kobayashi with Audi Le Mans star Andre Lotterer.