• Trump said he will send ICE agents to replace TSA at US airports on Monday.
• The largest federal workers union said ICE agents aren't trained for aviation security.
• More than 400 TSA officers have quit since mid-February amid the partial government shutdown.

America's largest federal employee union says ICE agents are unqualified to replace TSA officers at US airports.

"ICE agents are not trained or certified in aviation security. TSA officers spend months learning to detect explosives, weapons, and threats specifically designed to evade detection at checkpoints — skills that require specialized instruction, hands-on practice, and ongoing recertification," Everett Kelley, president of American Federation of Government Employees, said on Sunday in a statement posted online.

"You cannot improvise that. Putting untrained personnel at security checkpoints does not fill a gap. It creates one," he added.

The statement came one day after President Donald Trump said he would tap ICE agents to help with airport security as the partial government shutdown drags on.

"Likewise, I look forward to moving ICE in on Monday, and have already told them to,"GET READY." NO MORE WAITING, NO MORE GAMES!" Trump wrote on Truth Social.

White House Border Czar Tom Homan said Sunday that the administration was actively working on a plan to integrate ICE agents into airports.

"We'll have a plan by the end of today on what airports we're starting with and where we're sending them," Homan said on CNN's "State of the Union."

The partial government shutdown has left the Department of Homeland Security, which oversees the TSA, unfunded as Congress debates its immigration enforcement policies.

TSA officers haven't received a paycheck in five weeks, and more than 400 have quit since mid-February, according to The White House, compounding a staffing shortage. As a result, long wait times and massive lines are clogging airport security checkpoints.

On Sunday, Kelley said that many TSA agents have continued to show up to work despite the lack of pay. "They deserve to be paid, not replaced by untrained, armed agents who have shown how dangerous they can be," he said.

ICE has been at the center of Trump's immigration crackdown. Fatal shootings sparked widespread protests against the agency earlier this year and contributed to the removal of former DHS Secretary Kristi Noem.

Kelley called on Congress to "stop playing politics and do their jobs."

During an interview on Sunday, US Transportation Secretary Sean Duffy said TSA officers, whose salaries start around $40,000 annually, can't live on $0 paychecks.

"They're going to take other jobs to put food on the table and pay the rent," Duffy said on "This Week with George Stephanopoulos." "I do think it's going to get much worse, and as it gets worse, I think that puts pressure on Congress to come to a resolution."

Disruptions to air travel were what ultimately pushed Congress to end the previous full government shutdown.