The Trump campaign says it will refuse credentials to reporters with Bloomberg News, the outlet owned by Democratic presidental hopeful Michael Bloomberg.
After Mr Bloomberg’s official entry to the 2020 race last week, Bloomberg said it would stop critically covering the Democratic presidential candidates.
But the outlet said it would continue to investigate US President Donald Trump’s administration.
Mr Trump’s campaign called the Bloomberg decision proof of “bias”.
“Since they have declared their bias openly, the Trump campaign will no longer credential representatives of Bloomberg News for rallies or other campaign events,” said Mr Trump’s campaign manager, Brad Parscale, in a statement on Monday.
“We will determine whether to engage with individual reporters or answer inquiries from Bloomberg News on a case-by-case basis.”
The president and Mr Bloomberg have traded barbs ever since the former New York mayor began weighing his decision to run.
Announcing his candidacy, the billionaire businessman said he was standing in the race to “defeat Donald Trump”.
“The stakes could not be higher. We must win this election,” he wrote.
Just prior to Mr Bloomberg’s official entry, Mr Trump taunted “little Michael”, calling him a “nothing” and saying he “doesn’t have the magic” to make it to the White House.
The Trump campaign’s decision to revoke Bloomberg News’ press credential highlights the potential challenges faced by the outlet as its owner runs for president.