Twitter's new boss Elon Musk has asked staff to choose by Thursday between being "extremely hardcore" and working intense, long hours, or losing their jobs, according to an internal memo seen by AFP.
The Tesla tycoon has come under fire for radical changes at the social media company, which he bought for $44 billion late last month.
He has fired half of the company's 7,500 staff, scrapped a work-from-home policy, and imposed long hours, all while his attempts to overhaul Twitter have faced chaos and delays.
"Going forward, to build a breakthrough Twitter 2.0 and succeed in an increasingly competitive world, we will need to be extremely hardcore," Musk wrote in the internal memo.
"This will mean working long hours at high intensity. Only exceptional performance will constitute a passing grade," he added.
Staff have been asked to follow a link to affirm their commitment to "the new Twitter" by 5:00 pm New York time (2200 GMT) on Thursday.
If they do not do so, they will lose their jobs, receiving three months of severance pay.
Twitter did not respond to AFP requests for comment on the new measure.
Since Musk took over Twitter, his stumbling attempts to revamp user verification with a controversial subscription service have led to a slew of fake accounts and pranks, and prompted major advertisers to step away from the platform.
On Tuesday, Musk postponed the relaunch of Twitter's paid subscription service, Blue Verified.
Musk wants users to pay $8 for the coveted blue tick, which has until now been granted free to verified accounts, lending authority to public figures and media using Twitter.
However, the system was suspended as accounts impersonating others -- including Musk -- proliferated.
The relaunch is now set for November 29.
-'Somebody else' -
Musk on Wednesday said his overhaul of the company's "organization structure" would be done this week.
After "an initial burst of activity" to reorganize the company, "I expect to reduce my time at Twitter and find somebody else to run Twitter over time," he said.
Musk was speaking in a court hearing linked to his $50 billion pay package at Tesla, the electric car giant.
A shareholder has accused the South African multi-billionaire of being a part-time CEO for Tesla, saying that the board of directors did not sufficiently scrutinize the compensation.
Musk has warned Twitter's employees that the company risks bankruptcy if it is not quickly fixed.
In recent days, Musk has carried out more firings, sacking one engineer in a tweet after he openly criticized decisions under the new leadership.
"I would like to apologize for firing these geniuses. Their immense talent will no doubt be of great use elsewhere," Musk tweeted.