Republican National Committee Chairman Reince Priebus on Monday called on CNN and NBC to rethink their decisions to shoot films about Hillary Clinton, calling each a "thinly veiled attempt at putting a thumb on the scales of the 2016 presidential election."

Priebus also threatened, if the networks push forward with their plans, to avoid partnerships with them for any 2016 presidential debates.

Both networks announced their plans in recent weeks. CNN's documentary is set to run on TV and in theaters, while NBC's shooting a miniseries starring Diane Lane.

“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,” Priebus said in a statement. “Their actions to promote Secretary Clinton are disturbing and disappointing."

The letters were sent to Robert Greenblatt, chairman of NBC Entertainment, and Jeff Zucker, president of CNN Worldwide.

CNN, in a statement, said it won't back down and encouraged the RNC not to prejudge its documentary.

"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," CNN 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."

NBC News responded in a brief statement stressing it is not involved in the miniseries.

"NBC News is completely independent of NBC Entertainment and has no involvement in this project," it said.

But even as the networks press on, Priebus's effort is gaining traction in the GOP.

The chairmen of the Republican parties in Iowa and South Carolina -- two early states that generally hold multiple debates -- said they support Priebus's move.

"The Iowa GOP supports Reince Priebus in his decision and looks forward to helping the RNC start a new chapter in how Republicans across the country stand up to a biased media," Iowa GOP Chairman A.J. Spiker said in a statement.

David Plouffe, a former top adviser to President Obama, shot back, saying the RNC is trying to insulate itself from any media that isn't Fox News:

Priebus noted that Democrats complained when the conservative outside group Citizens United planned to air a pay-per-view documentary about Clinton on the eve of the 2008 election. The spat resulted in a landmark Supreme Court case that freed up donors to give large political contributions to so-called super PACs.

There was also a case in 2006 in which Clinton allies urged ABC to cancel a docu-drama called "The Path to 9/11," which depicted top Clinton aides undermining attempts to capture and kill Osama bin Laden.

Priebus pressured NBC and CNN to kill the documentaries quickly, giving them a deadline that is just nine days away.

"If they have not agreed to pull this programming prior to the start of the RNC’s Summer Meeting on August 14, I will seek a binding vote stating that the RNC will neither partner with these networks in 2016 primary debates nor sanction primary debates they sponsor," Priebus said.

Here's the CNN letter, courtesy of Zeke Miller:

CNN1 by Zeke Miller

Updated at 3:57 p.m.