Officials at Immigration and Customs Enforcement have been scrambling to carry out a weekend directive from President Trump to have immigration agents provide security at airports amid the partial government shutdown, multiple sources familiar with the internal deliberations told CBS News.

On Saturday, Mr. Trump posted a message on Truth Social suggesting he would deploy ICE agents to airports to conduct security and arrest people in the U.S. illegally, if congressional Democrats did not agree on a deal to fund the Department of Homeland Security. DHS oversees immigration agencies like ICE and the Transportation Security Administration. In subsequent posts, Mr. Trump said he would dispatch ICE agents to airports on Monday.

Mr. Trump’s directive caught officials at ICE off guard and they have been scrambling to come up with a plan to enforce it, the sources familiar with the matter told CBS News, requesting anonymity because they were not authorized to talk to the press.

“I have no idea what we’re doing,” one DHS source said when asked about the president’s order.

Lines at security checkpoints in airports across the country have increased in recent days, amid several hundred resignations and sick calls among TSA employees, who have been working without pay due to the partial shutdown.

Saturday marked the day with the highest number of nationwide call-outs when more than 3,250 employees called out. More than 400 officers have “separated” from the agency, DHS said. 

White House border czar Tom Homan told CNN on Sunday that he was working on a plan to execute the president’s directive, adding that he would be discussing the matter with the heads of TSA and ICE.

Homan suggested that ICE agents could provide site security at certain airports, as opposed to screening passengers and bags. He said having ICE agents secure exit and entry points at airports could allow more TSA agents to focus on screenings. Appearing on Fox News, Homan said ICE could also help by checking IDs.

Homan did not directly say whether any ICE agents dispatched to airports would also conduct immigration arrests, but noted they routinely enforce immigration laws there.

As federal immigration officers, ICE agents have the power under the Immigration and Nationality Act to arrest anyone, anywhere in the U.S., who they believe is in the country illegally or deportable on other grounds.

A former senior ICE official told CBS News that agents at the agency would probably not be equipped or trained to help with the more technical tasks of airport security, such as operating the screening machines. The former official said ICE agents could augment the security force at airports but that most other law enforcement agencies could as well.

Using Customs and Border Protection officers to bolster airport security, the former ICE official said, would make more sense, since many already operate at international airports, conducting immigration checks for incoming travelers.

In a statement to CBS News, DHS Acting Assistant Secretary Lauren Bis said: “While the Democrats continue to put the safety, dependability, and ease of our air travel at risk, President Trump is taking action to deploy hundreds of ICE officers, that are currently funded by Congress, to airports being adversely impacted.”

White House spokeswoman Abigail Jackson told CBS News that “the men and women of ICE are always prepared to help keep our country safe.”

“Americans are missing flights and hardworking TSA employees are missing paychecks — with over 400 TSA employees outright quitting,” she told CBS News. “Democrats could stop this all today by funding the Department.”

Congressional Democrats have declined to fully fund DHS unless the Trump administration agrees to make certain immigration enforcement reforms, including prohibiting ICE agents from wearing masks during operations.

The Flight Attendants Union urged lawmakers to pass the bill and pay TSA workers, calling the “latest threat of ICE invasion” at airports a “distraction from solutions that protect Americans.”

“(Transportation Security Officers) can’t simply be replaced,” the flight attendants’ union said in a statement, saying TSA workers go through rigorous training related to airport security that “ICE agents simply do not have and cannot learn quickly.”

“The introduction of ICE agents into airports creates contradictory missions, as attempts to question passengers about immigration status may distract them from ensuring airport security,” the statement said. “There’s one solution that immediately solves the problem at our airports. Pay the people who are already trained to protect us from terror attacks today, especially as the war with Iran increases the desire to strike against Americans.”