National Public Radio filed suit Tuesday against US President Donald Trump, seeking to block his order to end federal funding for it and the PBS television network.

Since returning to power in January, Trump has heightened his long-running feud with mainstream US media, which he accuses of being biased against him.

As part of an administration-wide media crackdown, officials have moved to outright dismantle government-funded news outlets, while the White House has revoked independent management of who covers its events.

Trump earlier this month signed an executive order directing the Corporation for Public Broadcasting, which oversees NPR and PBS, to stop giving them money.

The Trump administration said both "have fueled partisanship and left-wing propaganda with taxpayer dollars, which is highly inappropriate and an improper use of taxpayers’ money."

In its suit Tuesday, NPR argued that the Trump order violates the principle of separation of powers contained in the US constitution because it is Congress, not the White House, which controls the purse strings of federal funds.

The Corporation for Public Broadcasting budget has already been approved by Congress through 2027, which raises questions about the scope of Trump's order.

NPR said the order also violates the First Amendment guarantee of freedom of expression.

"The intent could not be more clear -- the Executive Order aims to punish NPR for the content of news and other programming the President dislikes," NPR CEO Katherine Maher said in a statement.

"We stand for constitutional rights, a free press, and an informed public, and we file today on their behalf," Maher added. 

She said 43 million people in America listen to NPR programs each week. PBS estimates 36 million watch its television programs on a local broadcaster every month.

The Trump administration is also moving to slash government spending drastically, firing tens of thousands of civil servants across many departments, often with little to no warning.

In the news media sector this has meant the elimination of government-funded news outlets projecting outside the United States such as Voice of America, Radio Free Asia and Radio Free Europe/Radio Liberty.

The Defense Department has also expelled several major national news outlets from their dedicated office spaces to make way for smaller, largely conservative sites.