New owner Elon Musk has told remaining Twitter employees they will need to decide by Thursday afternoon whether to stay at the company or quit.

In an email to staff entitled "A Fork in the Road," Musk said Twitter would "need to be extremely hardcore" to succeed. Those who choose to stay should expect long, intense hours of work. Those who leave will receive three months' severance pay, he wrote.

In the ultimatum, first reported by The Washington Post, Musk wrote that he values engineers over designers, project managers and other staff in what he envisions will be "a software and servers company."

The combative message is the latest sign of escalating tensions inside Twitter, a company that has been beset by chaos and confusion since the billionaire's $44 billion takeover in October.

Musk immediately fired top executives. Since then, he's laid off about half of the staff, or roughly 3,700 employees, and fired others after they publicly criticized him. People who held key roles in divisions including content moderation, cybersecurity and legal compliance have resigned.

Musk has claimed his shakeup is part of an effort to make Twitter more profitable, something that has long been a struggle for the platform. He also says the company needs to move away from advertising and derive most of its revenue from other sources, like Twitter Blue, the now-paused service that was revamped under Musk and had a tumultuous premiere.

One issue hanging over the company: its financial outlook now that it is newly saddled with debt.

Musk borrowed $13 billion to buy Twitter in a purchase widely seen as overpriced.

Ad sales, which make up nearly all of its revenue, have dropped as advertisers take a wait-and-see approach to both the broader economy and Musk's leadership of Twitter.

Meanwhile, Twitter is estimated to have a $1 billion debt service payment on the debt Musk secured to complete his takeover, and the company's ability to make that payment has been in question.

Musk has even floated the possibility of possible bankruptcy, which would allow Twitter to restructure its debt, but remains unclear how serious Musk was about that threat.

NPR's Bobby Allyn contributed to this story.