Brown told reporters at the U.S. Grand Prix that Indianapolis remained of interest and a decision would be taken once the Formula One season had ended.
"For the IndyCar series, we've taken the decision not to compete on a full time basis in 2019," said the American. "We're simply not ready yet and very focused on Formula One.
"We do have a desire to do it in the near future."
Brown had said in June that McLaren, Formula One's second most successful team in terms of races won but now struggling after a failed partnership with Honda, were strongly considering entering the U.S.-based IndyCar series.
There has been speculation that a team could be tailor-made for Fernando Alonso, the double world champion who is leaving Formula One at the end of the year and has set his sights on winning Indianapolis.
The Spaniard is chasing the 'Triple Crown of Motorsport', of which Indy is the last element after he won the Le Mans 24 Hours with Toyota this year.
Brown confirmed that Indianapolis was something Alonso would like to do.
Alonso competed in the race last year in an effort connected to Andretti Motorsport, leading before an engine failure ended his involvement.
McLaren won Indianapolis in 1974 and 1976 with Johnny Rutherford.
(Reporting by Alan Baldwin, editing by Pritha Sarkar)
