WASHINGTON (AP) — Federal immigration agents newly ordered to U.S. airports by President Donald Trump to help relieve security line congestion may guard exit lanes or check passenger IDs as a budget impasse has air travelers frustrated over hourslong waits and screeners angry about missed paychecks.

Trump made clear on Sunday, a day after saying he would use immigration officers for airport security starting Monday unless Democrats agreed on a bill to fund the Department of Homeland Security, 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, U.S. 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 showing no sign of backing down.

White House border czar Tom Homan, named by 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 characterized those sessions as “good conversations,” he said they were “not at a point yet where we’re in total agreement.”

The Senate, in a rare weekend session, advanced the nomination of Sen. Markwayne Mullin, R-Okla., to be Trump’s next homeland security secretary by a largely party-line vote, 54-37, with two Democrats joining Republicans. A vote on the confirmation could come as early as Monday as Mullin has tried to make the case that he would be a steady hand after the tumultuous tenure of Kristi Noem, Trump’s first DHS secretary.

Meantime, Homan said in Sunday news show interviews that the increased role of U.S. Customs and Immigrations Enforcement 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.”

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.” The priority, Homan said, 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,” Homan said, adding that “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.”