Image source, Reuters
By Ben Derico
BBC News, San Francisco
Elon Musk has said Apple has halted most of its advertising on Twitter and accused the company of threatening to remove the platform from its app store.
The feud comes as many companies have halted spending on Twitter amid concerns about Mr Musk's content moderation plans for the site.
Apple has been contacted by the BBC for comment.
Mr Musk has said Twitter has seen a "massive" drop in revenue, blaming activists for pressuring advertisers.
In a series of Tweets on Monday, he accused Apple of "censorship" and criticised its policies, including the charge it levies on purchases made on its app store.
"Apple has mostly stopped advertising on Twitter. Do they hate free speech in America?" he said.
He appealed directly to Apple's CEO - asking: "What's going on here @tim_cook?"
The owner of the social media platform also claimed Apple had threatened to withhold Twitter from its app store, but did not say why.
Mr Musk, who purchased Twitter for $44bn last month, is under pressure as some companies halt spending.
He has said he hopes to make money by turning Twitter verification into a paid subscription service, but currently the vast majority of the site's revenue comes from advertising.
Companies including Cheerios maker General Mills and Volkswagen are among the firms that have halted their spending in recent weeks.
Media Matters, a watchdog site, reported last week that half of Twitter's top advertisers had pulled their advertising on Twitter after concerns about the direction of Twitter.
Apple's media agency Omnicom recommended the Silicon Valley giant pause advertising on the platform out of concern for Apple's "brand safety", according to US tech site The Verge.
In picking a fight with Apple, Mr Musk is wading into a wider debate over the clout that Apple wields over online activity via its app store, which is the way that iPhone owners download games and other apps.
As it stands, Apple would take a 30% slice of the monthly fee Twitter plans to charge some users.
On Twitter, Mr Musk posted a meme saying "pay 30%. Go War" with an arrow pointing to the latter.
All companies listed in the app store have to abide by Apple's rules and pay its fees, or face removal or suspension.
Last year Apple suspended social media platform Parler from the store, saying it didn't do enough to remove hate speech.
Apple later restored Parler after the company updated its policies.