The largest federal government employee union is suing the Trump administration to block its buyouts for workers, calling the offer “an arbitrary, unlawful, short-fused ultimatum which workers may

The nation’s largest federal employee union is suing to halt the Trump administration’s voluntary resignation offer, arguing agencies can’t promise to pay employee salaries before Congress sets aside the money.

Senator Tim Kaine, Democrat of Virginia, quickly condemned the Trump administration’s offer to roughly 2 million federal employees to resign in exchange for pay, saying in a Senate floor speech that the deal was a trick, that the president didn’t have the authority to make the offer and employees who resign may not be paid.

President Donald Trump’s shutdown of the US Agency for International Development was challenged in court by unions representing federal employees, which say the freeze on foreign aid is causing a global humanitarian crisis and costing thousands of American jobs.

The suit says the administration's actions are costing thousands of jobs, threatening national security interests and causing a humanitarian catastrophe.

The largest U.S. government workers' union and an association of foreign service workers sued the Trump administration on Thursday in an effort to reverse its aggressive dismantling of the U.S. Agency for International Development.

The White House is slashing the USAID workforce. Trump's funding freeze is also stalling federal firefighter hiring. NBC News correspondents Kelly O'Donnell, Sahil Kapur and Jacob Soboroff have the latest reporting.

The lawsuit is the first seeking to block the Trump administration's overhaul of the US Agency for International Development.