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

The Treasury Department's Office of Inspector General and the Government Accountability Office confirmed it will investigate reported access to the Treasury's vast payment systems by DOGE employees.

The Treasury's deputy inspector general wrote in a letter to lawmakers that she initiated an audit on Feb. 6 and they "expect to begin our fieldwork immediately."

"Given the breadth of this effort, the audit will likely not be completed until August; however, we recognize the danger that improper access or inadequate controls can pose to the integrity of sensitive payment systems. As such, if critical issues come to light before that time, we will issue interim updates and reports," the deputy inspector general added.

The letter came after Democratic senators last week raised concerns about DOGE's access to Treasury data.

-ABC News' Allison Pecorin

Ukrainian President Volodymyr Zelenskyy said the United States, including the Biden administration, never saw Ukraine as a NATO member.

Zelenskyy made the comments while speaking at the Munich Security Conference in Munich ahead of a planned meeting with Vice President JD Vance.

"I heard so many times from the American side, by the way, Biden's administration and now from President Trump. I heard a lot of messages from them by phone. My first phone call with President Biden and my first question, will we be in NATO? He said, no, no. And I said, we will see," Zelenskyy said.

"But to be very honest, United States, they never saw us in NATO. They just spoke about it. But they really didn't want us in NATO. It's true," Zelenskyy added.

Zelenskyy reiterated that if they cannot join NATO, they will build their own version within Ukraine. Zelenskyy said he doesn't "want to be that person in history who helped Putin to occupy my country."