The time-honored tradition of US presidential debates could be at risk.

The Republican National Committee (RNC) is threatening to boycott the debates unless the body that organizes them changes its rules.

US presidential and vice presidential debates have been sponsored for the past three decades by the nonpartisan Commission on Presidential Debates (CPD).

In a letter to the CPD on Thursday, RNC chair Ronna McDaniel accused the commission of "stonewalling the meaningful reforms necessary to restore its credibility with the Republican Party as a fair and nonpartisan actor."

Absent the reforms, "the RNC will take every step to ensure that future Republican presidential nominees are given that opportunity (to debate) elsewhere," McDaniel said.

"Accordingly, the RNC will initiate the process of amending the Rules of the Republican Party at our upcoming Winter Meeting to prohibit future Republican nominees from participating in CPD-sponsored debates," she said.

McDaniel complained in her letter that the first debate between Republican Donald Trump and Democrat Joe Biden in 2020 was held after early voting had already begun.

She said the commission had made "unilateral changes to previously agreed-upon debate formats and conditions" and selected a moderator "who had once worked for the Democrat nominee."

In addition, she said a majority of the CPD board members had been "publicly disparaging" of Trump, the Republican nominee.

In a statement to The New York Times, the CPD said it "deals directly with candidates for President and Vice President who qualify for participation."

"The CPD's plans for 2024 will be based on fairness, neutrality and a firm commitment to help the American public learn about the candidates and the issues."

The commission has sponsored the US presidential debates since the 1988 election.