The designation of "state-affiliated media" for Washington-based National Public Radio -- a label also applied to government-owned Chinese and Russian outlets -- comes just days after Twitter stripped The New York Times of its verified status on the platform, the first sign of Musk's updated policies for news media.

Both US news organizations are often considered by conservatives as bastions of a left-leaning media establishment, a position often echoed by Musk in tweets.

According to Twitter policy, the decisions will deamplify tweets from both companies, limiting their reach on a platform that remains a major communication tool for media outlets, celebrities and officials.

Musk had set an April 1 deadline for individuals and companies to either pay for verification on Twitter or see their "verified" status removed, though many check-marks remained for non-paying customers days later.

NPR's main account, which still has a check-mark, was tagged Tuesday night as "state-affiliated media," a designation that also applies to Chinese public broadcaster CCTV and Moscow's RT network.

"We were disturbed to see last night that Twitter has labeled NPR as 'state-affiliated media,' a description that, per Twitter's own guidelines, does not apply to NPR," said the broadcaster's president and CEO John Lansing.

Lansing said that NPR was "supported by millions of listeners who depend on us for the independent, fact-based journalism we provide."

According to NPR's website, the bulk of its budget comes from fees paid by member stations throughout the United States, who are themselves supported by individual donors and government funds.

The broadcaster told AFP less than one percent of its operational budget comes from federal sources.

"NPR stands for freedom of speech and holding the powerful accountable. It is unacceptable for Twitter to label us this way," Lansing said.

In an explanation of its policy, Twitter states on its website that state-affiliated media "is defined as outlets where the state exercises control over editorial content through financial resources, direct or indirect political pressures, and/or control over production and distribution."

But as of Wednesday afternoon, Twitter's Help Center continued to explicitly specify that NPR should not fall under that designation.

"State-financed media organizations with editorial independence, like the BBC in the UK or NPR in the US for example, are not defined as state-affiliated media for the purposes of this policy," it said.

Other accounts run by NPR, such as its music and politics handles, did not have the "state-affiliated" specification as of Wednesday afternoon.

Free speech advocacy organization PEN America slammed the move as dangerous.

"For Twitter to unilaterally label NPR as state-affiliated media, on par with Russia Today (RT), is a dangerous move that could further undermine public confidence in reliable news sources," said the group's digital policy manager Liz Woolery.