"He likes the series but hasn't decided yet what he wants to do as it relates to formula one. But our decision is not Fernando dependent," he told the Indy Star.
Brown is referring to McLaren's own deliberations, as talks with Michael Andretti's Indycar outfit about a team collaboration take place.
Andretti has even set a mid-August deadline.
"I hadn't heard that he put a date out there," Brown said. "But we are going to have to make a decision soon.
"Right now, we're laser-focused on formula one. We have driver decisions to make. We just hired a new technical director.
"That being said, we feel we still have time to make a decision on Indycar for 2019."