Fernando Alonso's hopes of competing in a third Indianapolis 500 in 2020 has been dented after Honda blocked a deal with Andretti Autosport.

The two-time Formula 1 champion is only a victory at the Brickyard away from becoming just the second driver after Graham Hill to win motorsport's Triple Crown.

But his first two attempts have both ended in failure, with an engine failure ending his debut in 2017 and operational issues at McLaren meaning Alonso failed to even qualify in 2019.

For his third trip, the Spaniard had reportedly already agreed to return to Andretti Autosport for Indy and an announcement was expected last week.

But when Honda's Performance Development division sought permission from their Japanese bosses in Tokyo, RACER reveals the answer was no.

It is also understood Alonso was in talks to stay with the team and compete in several road course events this season.

The repercussions of Honda vetoing a deal means the 38-year-old will now have to find a Chevrolet-backed team to enter this year's Indy 500.

One potential option could ironically be McLaren's new full-time IndyCar team, Arrow McLaren SP, this after the British team partnered up with Schmidt Peterson Motorsport for 2020 and beyond.

If not, four other squads are believed to have seats available where Alonso could join, safe from Honda's wrath.