Business and government accounts on Twitter could be facing “a slight cost” to stay on the social media platform following Elon Musk’s takeover.
The prospective Twitter owner and Tesla boss said the site would always be free for “casual users.”
It comes after Mr Musk agreed a £34.5 billion takeover deal with the Twitter board last month.
He said at the time he was looking forward to “enhancing the product with new features”, as well as improving the website’s free speech principles.
His takeover is expected to be completed later this year.
Twitter has already launched a premium, subscription-based version of the service in some countries, where users can pay a monthly fee to access additional features to “customise their Twitter experience,” including an Undo Tweet tool.
The billionaire has said he also wants to eradicate spam bots from the site and “authenticate all humans”, and has expressed support for a tool to edit already posted tweets – something Twitter had previously confirmed was already in development.
On Tuesday, the social media platform announced a trial of another new feature – Twitter Circle – which will enable users to share tweets with a smaller crowd of up to 150 selected users.
The tool is now being rolled out to some users for testing, with Twitter saying it builds on the idea that “some tweets are for everyone and others are just for people you’ve picked”.
It has been compared to the Close Friends feature on Instagram, which also allows users to share content with a select group of people rather than be posted publicly.
Mr Musk is the world’s richest person, worth an estimated £243 billion.