The Commission on Presidential Debates issued a statement after GOP candidate Donald Trump said the fall debate schedule was “rigged” and “unacceptable.”

In a tweet storm typical of the GOP frontrunner, Trump said Friday night that Hillary Clinton and the Democratic Party are “trying to rig the debates.”

As usual, Hillary & the Dems are trying to rig the debates so 2 are up against major NFL games. Same as last time w/ Bernie. Unacceptable! — Donald J. Trump (@realDonaldTrump) July 30, 2016

Yet the schedule was determined by the Commission last year, as it always is before presidential election years.

The Commission released a statement explaining their process when picking the debate dates for this fall:

“The Commission on Presidential Debates started working more than 18 months ago to identify religious and federal holidays, baseball league playoff games, NFL games and other events in order to select the best nights for the 2016 debates. It is impossible to avoid all sporting events, and there have been nights on which debates and games occurred in most election cycles. A debate has never been rescheduled as a result. As a point of reference, in a four-year period, there are four general election debates (three presidential and one vice presidential) and approximately 1,000 NFL games. The CPD selects the debate dates a year in advance in order for the television networks to have maximum lead time and predictability in scheduling these extremely important civic education forums. The CPD believes the dates for the 2016 debates will serve the American public well.”

The CPD was specifically formed as a nonpartisan group to create a structure for debates that doesn’t favor one candidate over another.

Officials from both parties are not involved in the scheduling process, as reported by CNN.

Trump’s debate disappointment leads some to believe that he may threaten to skip a general election debate, similar to how he skipped one of the GOP primary debates in January.

He also told ABC News he received a letter from the NFL that said the debate dates were “ridiculous” because two of the debates will be held during NFL games.

A spokesperson from the NFL said, “While we’d obviously wish the debate commission could find another night, we did not send a letter to Trump.”

CNN contributed to this report.