The head of the Republican Party threatened Monday to cut out CNN and NBC from the GOP presidential primary debates if the networks do not shelve their plans to air lengthy features on Hillary Clinton -- who is widely expected to be a Democratic candidate in the 2016 election.

Republican National Committee Chairman Reince Priebus accused both networks of trying to put "a thumb on the scales" of the 2016 race with programming he claimed would be tantamount to an "in-kind donation" to the Clinton campaign.

Last month, CNN Films announced it was producing a documentary on Clinton to premiere next year, first in theaters and then on CNN.

NBC also announced a four-hour "Hillary" miniseries starring Diane Lane, on the life of the former secretary of state and first lady.

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Priebus' statement on Monday marked the most aggressive challenge yet to those plans.

In a written statement, Priebus said if the networks don't meet his demands, he will seek a "binding vote" at the upcoming Aug. 14 RNC meeting declaring that the party "will neither partner with these networks in 2016 primary debates nor sanction primary debates they sponsor."

"It's appalling to know executives at major networks like NBC and CNN who have donated to Democrats and Hillary Clinton have taken it upon themselves to be Hillary Clinton's campaign operatives," he said.

In letters to the heads of both networks, Priebus said the Clinton specials would be unfair not only to Republicans, but to Democratic candidates who might also compete in the primary -- including Vice President Biden and Maryland Gov. Martin O'Malley. (Read the letters here and here.)

"Secretary Clinton has been in the public eye for well over two decades, so you certainly cannot claim that a series about her political career is any sort of public service or informational docudrama on an unknown individual," Priebus wrote. "Quite the opposite is true: it would be most accurately described as an in-kind donation.

"Out of a sense of fairness and decency and in the interest of the political process and your company's reputation, I call on you to cancel this political ad masquerading as an unbiased production."

CNN defended its planned documentary in a written statement released Monday afternoon.

"This documentary will be a non-fiction look at the life of a former First Lady and Secretary of State. Instead of making premature decisions about a project that is in the very early stages of development and months from completion, we would encourage the members of the Republican National Committee to reserve judgment until they know more," the statement said. "Should they decide not to participate in debates on CNN, we would find it curious, as limiting their debate participation seems to be the ultimate disservice to voters."

The RNC letters were addressed to NBC Entertainment Chairman Robert Greenblatt and CNN Worldwide President Jeff Zucker.