More than 300 news outlets are launching a campaign on Thursday to counter President Donald Trump’s attacks and promote a free press.
The Boston Globe made the call last week for a nationwide denouncement of the president’s “dirty war” against the media, using the hashtag #EnemyOfNone.
Mr Trump has derided media reports as “fake news” and attacked journalists as “enemies of the people”.
UN experts have said this raises the risk of violence against journalists.
The Boston Globe had pledged to write an editorial “on the dangers of the administration’s assault on the press” on 16 August, and asked others to do the same.
The initial positive response from 100 news organisations has grown closer to 350 with major US national newspapers and smaller local outlets answering the call, along with international publications like the UK newspaper The Guardian.