And for those who choose it, "there will be a higher priced subscription that allows zero ads," Musk added.
That would be a radical change in business model from Twitter, which has so far relied on targeted advertising to generate revenue, before launching a paid subscription service in mid-December.
But advertising has been a question mark for Twitter lately, after Musk fired about half of the company's 7,500-strong workforce late last year. The move sparked concern that the company was insufficiently staffed to carry out content moderation and spooking governments and advertisers.
Musk said his strategy was to massively reduce costs while building up revenue, and that a new subscription service called Twitter Blue, which grants users a sought-after blue verification tick for a fee, would help reach that goal.
The service costs $11 a month in the United States and is available on Apple's iOS and Google's Android mobile operating systems, according to a page on the company's website.
Web subscriptions are also available for $8 per month or, at a discount, $84 per year.
Twitter Blue is currently available in the United States, Canada, Britain, New Zealand, Australia and Japan.
Musk-led Twitter has been riven by chaos, with mass layoffs, the return of banned accounts and the suspension of journalists critical of the South African-born billionaire.
Musk's takeover also saw a surge in racist or hateful tweets, drawing scrutiny from regulators and chasing away big advertisers, Twitter's main source of revenue.