Twitter has hidden a tweet by President Donald Trump from his profile, saying it violates rules about glorifying violence.
It did the same hours later when the official White House account tweeted a copy of the president’s words.
Instead of being deleted, both tweets can be viewed by clicking on a prominent warning.
It says that “Twitter has determined that it may be in the public’s interest for the Tweet to remain accessible.”
It is the latest in an escalating row between Twitter and the White House.
Mr Trump was tweeting about the US city of Minneapolis, which has seen consecutive nights of protests following the death of a black man in police custody.
The president said he would “send in the National Guard”, and followed that up with a warning that “when the looting starts, the shooting starts.”
That second tweet was hidden by Twitter for “glorifying violence”.
Twitter’s policy of adding a warning to, rather than deleting, tweets that break its rules when it comes to major public figures was announced in mid-2019. But the social network has never used it on Mr Trump – nor deleted any of his tweets before.
“This is the bravest and riskiest thing I’ve ever seen Twitter – or any social media giant – do,” said Carl Miller, from the Centre for the Analysis of Social Media at UK-based think-tank Demos.
“This pours rocket fuel over the online-harm-versus-free-speech debate. Online content policy doesn’t get more incendiary than this.”
The same post remains unaltered on Facebook, without any warning attached.
The move means that other users will not be able to like, reply, or retweet it, Twitter said – but would still be able to retweet with a comment attached.
In a Twitter thread, the social network said: “This tweet violates our policies regarding the glorification of violence based on the historical context of the last line, its connection to violence, and the risk it could inspire similar actions today.”
Hours after the warning was added, President Trump tweeted: “Twitter is doing nothing about all of the lies & propaganda being put out by China or the Radical Left Democrat Party” and alleged that the social network was targeting Republicans.