Fernando Alonso races at the Indy 500 this year, missing the Monaco Grand Prix.
The Spaniard, who has signed to race again with McLaren next season, is supposedly eyeing a run at Le Mans.
And while 2017 world champion Hamilton has given Alonso his blessing, the Brit doesn’t think it’s the best idea.
“I admire what Alonso wants to do, but for me, Formula 1 is the maximum experience a driver can have,” Hamilton told Brazilian outlet UOL.
“A great driver, if he cannot win in Formula 1, will look for other races to win.
“But to see Alonso (finish) fifth (in the Indy 500) against drivers who are there all year is… interesting.”
Hamilton’s comments echo what he said in October, when he described his lack of desire to race the other two legs of motorsport’s Triple Crown as “a shame”.
Hamilton claimed 10 race wins this year and is favourite to clinch a fifth Drivers’ Championship crown in 2018.
Red Bull and Ferrari are expected to gain ground on Hamilton’s Mercedes, while McLaren could pose a threat with their new Renault engine.
And the 32-year-old wants himself and team-mate Valtteri Bottas to improve on 2017 before they are caught.
“It has been an amazing season but by no means a perfect one,” said Hamilton.
“There are always areas you can improve on.
“I won nine races and Valtteri Bottas won three — but there are 20 races and a perfect season is when you win every single one of them.
“But it’s a positive thing because it means you can always improve.
“When I’m preparing for a season, I firmly believe that we can be contenders for the next championship.”