Porsche and Red Bull had been discussing a partnership for months but talks ended in September with the team determined to stay independent.
The carmaker said at the time that the series remained "an attractive prospect" it would continue to monitor, with fellow Volkswagen-owned brand Audi already committed to enter from 2026 when engine rules change.
"At Spa-Francorchamps in August, Audi announced it was joining the FIA Formula One World Championship from 2026 as a power unit manufacturer," the FIA said in a statement after a meeting of its World Motor Sport Council in London.
"This announcement was an endorsement of the hard work by all stakeholders to develop those (new power unit) regulations.
"We also note that Porsche are still in discussions with Formula One teams."
Porsche was listed in Frankfurt last month in Germany's biggest initial public offering (IPO) in more than 25 years.
