Twitter has launched a new feature that lets users post tweets that disappear after a day.

The social media company calls the new tweets "fleets." The word fleet is an adjective meaning very fast or quick. Fleets can be sent as written messages, pictures or videos.

Twitter says it decided to add the feature after some users expressed concerns about the current tweeting system.

"Some of you tell us that tweeting is uncomfortable because it feels so public, so permanent," the company said Tuesday in an announcement on its website. Some users also feel a lot of pressure to receive large numbers of likes and retweets, it added.

Fleets cannot be retweeted and will not have likes. The only way a person can answer or comment on a fleet is by sending the user a direct message. This prevents any back-and-forth communication between users from becoming a public discussion.

"To help people feel more comfortable, we've been working on a lower pressure way for people to talk about what's happening," Twitter said. Fleets were launched "so everyone can easily join the conversation in a new way – with their fleeting thoughts."

The new Twitter feature comes long after other social media services – including Snapchat, Facebook and Instagram – added the ability for users to send disappearing messages. Such messages have become increasingly popular with social media users looking for smaller groups or more private messaging.

The company had been testing the feature in Brazil, Italy, India and South Korea before launching it worldwide.

"Those new to Twitter found fleets to be an easier way to share what's on their mind," the Twitter statement said. "Because they disappear from view after a day, fleets helped people feel more comfortable sharing personal and casual thoughts, opinions, and feelings."

However, some Twitter users who experimented with the feature said they were worried that the tool may create new possibilities for online abuse. For example, they said fleets could permit the sending of unwanted direct messages. The feature also permits fleet writers to "tag" people who have blocked them.

A Twitter official told Reuters news agency it was listening to suggestions from users and would work to fix safety concerns like the blocking issue.

Twitter and other social media companies are under pressure to do a better job of preventing abuses and limiting the spread of misinformation on their websites.

Another new Twitter feature set to launch to all users next year is the "voice tweet," an audio recording that takes the place of a written message. The company's product designer, Maya Gold Patterson, said many users feel Twitter's 280-character message model is too limiting.

"And sometimes tweeting isn't the right way of communicating at the moment," Patterson said. "So we were interested in exploring how audio could help add an additional layer to the public conversation." The feature has been tested in recent months.

Twitter also confirmed plans to launch a live audio feature, called "Spaces." This tool will permit users to talk in public, group conversations. It is similar to Clubhouse, a social service in which users are invited to hold conversations in voice chat rooms.

I'm Bryan Lynn.

Bryan Lynn wrote this report based on reports from The Associated Press, Reuters, Agence France-Presse and Twitter. Caty Weaver was the editor.