The administration of U.S. President Donald Trump on Monday locked U.S. Agency for International Development workers out of their headquarters in downtown Washington as it moved to shutter the agency, prompting two Democratic senators to vow to block confirmations of State Department nominees in protest.

The lockout added to the chaos that has consumed the agency, which distributes billions of dollars of humanitarian aid around the world, since Trump ordered a freeze on most U.S. foreign aid hours after taking office on Jan. 20.

USAID has also been targeted for closure by billionaire Elon Musk, who has been tasked by the president with downsizing the federal government. A senior White House official, speaking on condition of anonymity, said Trump was considering merging USAID into the State Department and had "entrusted Elon to oversee the efficiency of this agency."