U.S. District Court Judge Tanya Chutkan has scheduled a 4 p.m. initial hearing on Elon Musk's authority to run the Department of Government Efficiency.

Fourteen states are challenging Musk's role overseeing DOGE and accusing him of being a "designated agent of chaos" whose "sweeping authority" is in violation of the U.S. Constitution. Musk has defended his position by describing his role as the country's "volunteer tech support guy."

Read more about the lawsuit here.

-ABC News' Katherine Faulders

The Department of Energy has paused the firings of hundreds of employees who work for a key agency maintaining the U.S. nuclear weapons stockpile, multiple sources tell ABC News.

Managers with the National Nuclear Security Administration (NNSA) are frantically calling employees back and telling them that -- as of right now -- they're not fired, despite some receiving termination emails and phone calls on Thursday. Their badges are getting turned back on and access to federal systems is being restored, at least temporarily.

Hundreds of probationary employees were terminated Thursday night in the mass Trump administration layoffs. The move prompted concerns of a national security risk because the agency is responsible for maintaining U.S. nuclear weapons, transporting them, and nuclear counterterrorism, among other missions.

NNSA held an all-staff meeting Friday morning, announcing the DOE had agreed to pause the layoffs, due to the agency's national security mission.

NNSA staff tell ABC News they are in a holding pattern. They're still bracing for firings, but possibly not as widespread.

-ABC News' Jay O'Brien

Vice President JD Vance and Ukraine President Volodymyr Zelenskyy met on Friday on the sidelines of the Munich Security Conference.

Both men characterized the meeting as the starting point for negotiations to end the war in Ukraine that began with Russia's full-scale invasion nearly three years ago. Zelenskyy said the conversation was "good" and said they want to achieve peace but that Ukraine requires "real security guarantees."

Hundreds of staff at the agency responsible for maintaining the U.S. nuclear stockpile were fired Thursday in the wave of mass Trump administration terminations, multiple current and former employees told ABC News.

The National Nuclear Security Administration ensures "the United States maintains a safe, secure, and reliable nuclear stockpile," according to its website. The agency also has a team of first responders that deploy to nuclear disasters around the globe and a counterterrorism division, which hunts down nuclear devices in the hands of U.S adversaries.

All of those key functions were impacted by the firings, ABC News' Jay O'Brien was told.

Multiple current and former employees described the situation as "a national security crisis."

Two former staffers confirmed probationary employees began receiving termination notices late Thursday and worried the agency of only about 1,800 employees was losing the key nuclear arms expertise that cannot be replaced.

-ABC News' Jay O'Brien