Lewis Hamilton has apparently scoffed at the level of competition facing Fernando Alonso ahead of Sunday's Indy 500.

Not long after this weekend's prestigious Formula 1 race, Monaco absentee Alonso will start from fifth as he bids to win the fabled Indy 500 on the other side of the Atlantic.

Hamilton, however, does not seem to rate Alonso's full-time Indycar competitors.

"I looked at the times and, frankly, for his first ever qualifying for Fernando to be fifth - what does that say about Indy?" the Mercedes driver told France's L'Equipe.

However, Hamilton defended his former McLaren teammate's decision to tackle Indy.

"A great driver, if he cannot win in Formula 1, will look for other races to win," he said. "But to see him fifth against drivers who are there all year is... interesting."

Alonso has been unable to pick up any points at McLaren so far in 2017.