Immigration and Customs Enforcement (ICE) agents newly ordered to US airports to help relieve security line congestion may guard exit lanes or check passenger IDs.

President Donald Trump ordered ICE agents to airports as a budget impasse had air travellers frustrated over hours-long waits and screeners angry about missed paycheques.

Mr Trump made clear on Sunday, a day after saying he would use immigration officers for airport security starting on Monday unless Democrats agreed on a bill to fund the Department of Homeland Security (DHS), that he was going ahead with the plan to assist the Transportation Security Administration.

Hundreds of thousands of homeland security workers, including from the TSA, US Secret Service and Coast Guard, have worked without pay since Congress failed to renew DHS funding last month. 

Democrats are demanding major changes in the conduct of federal immigration agents and are showing no sign of backing down.

White House border czar Tom Homan, named by Mr Trump to lead this effort, has also been meeting with a bipartisan group of senators in recent days over the partial shutdown and while he characterised those sessions as “good conversations,” he said they were “not at a point yet where we’re in total agreement”.

A large crowd at an airport security point.

American travellers are experiencing long waits to clear security amid an ongoing dispute over Homeland Security funding. (AP: Yuki Iwamura)

The Senate, convening in a rare weekend session, was expected to advance the nomination of senator Markwayne Mullin to be Mr Trump’s next homeland security secretary. 

A vote on the confirmation could come as early as late on Monday local time as Senator Mullin has tried to make the case that he would be a steady hand after the tumultuous tenure of Kristi Noem, Mr Trump’s first DHS secretary.

Meanwhile, Mr Homan said in Sunday news show interviews that the increased role of US Immigration and Customs Enforcement (ICE) officers at airports — specific duties and numbers — was subject to discussions with the leadership of TSA and ICE “to find out where we can fit in”.

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He pledged to have “a plan by the end of today, where we’re sending — what airports we’re starting with and where we’re sending them”. 

“So it’s a work in progress,” he said. 

Mr Homan said the priority was “the large airports where there’s a long wait, like three hours”.

Immigration officers, as an example, could cover exits currently monitored by TSA agents, freeing them to work screening lines.

“ICE agents are assigned at many airports across the country already. They do a lot of investigation, criminal investigation on smuggling at airports,” Mr Homan said.

“Certainly, a highly trained ICE law enforcement officer can cover an exit and makes sure people don’t go through those exits, entering the airport through the exits. And stuff like that relieves that TSA officer to go to screening and to reduce those lines.”

Another option, he said, was having ICE agents check identification before people enter screening areas.

A man faces a group of federal agents with their faces covered

The conduct of ICE agents has been under scrutiny after the killing of two American citizens during a crackdown in Minnesota. (Reuters: Leah Millis)

Huge queues snake through terminals

Travellers at some airports worried about reaching their gates on Sunday.

At Atlanta’s Hartsfield-Jackson International Airport, lines wrapped from one end of the airport to the other. 

“Everyone just seems to be accepting it for what it is,” said 43-year-old Blake Wilbanks, who showed up two-and-a-half hours early for his morning flight to Salt Lake City after reading about the shutdown.

“Hopeful I’m gonna make it,” he said as he waited in a winding security line.

The scene appeared more chaotic at John F Kennedy International Airport in New York. Large crowds of anxious travellers piled toward security checkpoints, and TSA staff shouted through megaphones to tell people not to push one another.

For Transportation Secretary Sean Duffy, one concern is the uncertainty that passengers are facing over possible wait times at any airport on any given day.

“Do I have to come an hour and a half early? Do I have to come four hours early? They don’t know until the day of or the afternoon of their flight,” he said. 

“So if we can alleviate that, again, the president wants to take away that leverage point for Democrats and make travel easier for the American people.”

House Democratic leader Hakeem Jeffries said “the last thing that the American people need are for untrained ICE agents to be deployed at airports all across the country” after criticism about their conduct as part of Mr Trump’s immigration enforcement operations in Minnesota and elsewhere.

AP