The chief of the criminal division at the U.S. Attorney's Office for Washington, D.C., abruptly resigned Tuesday amid pressure from top Trump Justice Department appointees to freeze assets stemming from a Biden administration-era environmental initiative, sources familiar with the matter told ABC News.

A resignation letter sent to the office's employees by prosecutor Denise Cheung did not detail specific reasons for her sudden departure from the office, but encouraged prosecutors to continue adhering to the Constitution.

The move came just one day after President Donald Trump announced Ed Martin as his nominee for D.C. U.S. Attorney.

-- ABC News' Alexander Mallin and Katherine Faulders

Vice President JD Vance will speak at the Conservative Political Action Conference (CPAC) on Thursday, a source familiar confirmed to ABC News.

Vance spoke at the event last year, where much of his speech centered around foreign policy. The vice president recently spoke at the Munich Security Conference, where he stoked controversy by focusing much of his remarks on criticizing European allies.

-ABC News' Hannah Demissie

Following their meeting with a high-level Russian delegation in Saudi Arabia, Secretary of State Marco Rubio said top on the agenda would be restoring U.S. and Russian diplomatic missions in Washington and Moscow, which have been reduced to skeleton staffs due to reciprocal cuts over the course of the last decade.

The secretary said both the U.S. and Russia would "appoint a high-level team to negotiate and work through the end of the conflict in Ukraine in a way that's enduring an acceptable to all parties engaged."

Rubio remained vague when asked about what concessions they expect Russia to make, and if sanctions on Russia should or would be lifted.

"Again, we're not going to pre-negotiate nor an end to this conflict. These are the kinds of things that have to happen through hard and difficult diplomacy in closed rooms over a period of time," Rubio said.

Steve Witkoff, special envoy to the Middle East, also described the meeting as "positive, upbeat, constructive," and "solution-based."

– ABC News' Shannon Kingston

As Elon Musk's DOGE continues to target federal agencies like the Social Security Administration and Internal Revenue Service, the world's richest man has now set his sights on U.S. gold reserves at Fort Knox.

In recent days, Musk repeatedly posted about wanting to "make sure" the gold is still at the United States Bullion Depository at Fort Knox, Kentucky, which holds approximately 147.3 million ounces of gold, according to the U.S. Mint.

Musk has cast doubt on whether the gold remains at Fort Knox, writing on X: "This gold is the property of the American people. I sure hope it's still there!"

"Who is confirming that gold wasn't stolen from Fort Knox?" Musk also posted.

Former Treasury Secretary Steven Mnuchin visited the facility in 2017 during President Donald Trump's first administration. The vault was last opened to journalists and a congressional delegation back in 1974. According to the U.S. Mint website, "The Treasury Secretary allows the visit when rumors persist that all the gold had been removed from the vaults."

Musk on Monday even floated the idea of live-streaming a walkthrough of Fort Knox, responding to conspiracy theorist Alex Jones' coverage of his comments by suggesting he'd like to film inside the vaults.

-ABC News' Will Steakin