Motorsport.com understands Ericsson will be at Spa on duty for the Alfa Romeo team, with which he is official third and reserve driver.

Sources have indicated there may be an issue that could prevent the team's regular race driver Kimi Raikkonen from competing and Ericsson was understood to be travelling to Belgium on Thursday morning.

Ericsson lost his drive at the Sauber team after the 2018 season, while Raikkonen and Antonio Giovinazzi formed an all-new line-up as the entry adopted the Alfa name for 2019.

The Swede has remained associated with Alfa and dovetailed his reserve role with a full-time IndyCar programme in the United States.

Raikkonen and Giovinazzi were named on Alfa’s official media schedule for the Belgian GP earlier this week, while Ericsson should be in Portland for the next round of his rookie Indy campaign.

However, his Schmidt Peterson Motorsports IndyCar team has confirmed in a statement that Ericsson was released for his driving duties for Portland "following a request from Alfa Romeo Racing" for the Swede to be present at Spa.

SPM has thus already named Conor Daly as Ericsson's replacement for the Portland round.

Alfa released its official race preview on Thursday, with both normal race drivers quoted and no indication of an impending change.

When contacted by Motorsport.com, the team maintained that there was no plan for Ericsson to race at Spa, and that he was simply required as cover because the outfit did not have any alternative options for the Belgian round.

F1’s rules give teams until Friday to decide who will take part in practice - and should Ericsson replace Raikkonen for Friday running, the rules would still allow Raikkonen to return on Saturday and complete the remainder of the weekend.

Marcus Ericsson, Arrow Schmidt Peterson Motorsports Honda Photo by: Phillip Abbott / LAT Images

Ericsson has had a difficult first season in IndyCar, scoring a podium finish with second place in Detroit but lying only 17th in the championship after multiple missed opportunities.

His future in the series was thrown in doubt following the announcement of his Schmidt Peterson team’s collaboration with McLaren for 2020.

Ericsson left F1 after his most competitive season to date, having scored points in six races, but also trailed rookie teammate Charles Leclerc 39 points to nine in the final standings.

Should Ericsson return to F1 action he would have the opportunity to score points again immediately, as Alfa is one of the most competitive cars in the midfield.

He has already driven the car this year, in a Pirelli tyre test in Austria.

Alfa is locked in a fierce fight for fifth in the constructors’ championship but the points disparity between its two drivers means the team is only seventh, eight points behind Renault and 12 points behind Toro Rosso.

Raikkonen has enjoyed a fine first season at Alfa since leaving Ferrari, scoring 31 points to lie eighth in the championship.

However, Giovinazzi has struggled, and is 18th in the standings with just one point to his name.