Sick days among Transportation Security Administration employees have increased since a partial government shutdown beginning Dec. 22 left TSA personnel working without pay, the agency announced Friday.

An increase in call-outs — workers who say they are too sick to work their shifts —started over the holidays and has grown, but the phenomenon is causing a "minimal impact" on the security screening process at airports, the agency says in a tweet.

"Security effectiveness will not be compromised and performance standards will not change . . . To date, however, screening wait times remain well within TSA standards," the statement said.

The information was released as a response to a CNN report saying mass TSA worker call-outs had affected four major airports. The New York Times also reported on the call-outs.

Of the 2.2 million passengers screened by the agency Thursday, 99.8 percent waited less than 30 minutes, according to the TSA statement.

As the shutdown is headed towards a third week, tens of thousands of TSA agents are among federal employees who are working without pay.

President Donald Trump and lawmakers emerged Friday afternoon from their latest round of talks at the White House, only to indicate that an agreement to end the partial shutdown could be a long way off.

Trump, who has demanded $5.6 billion to help pay for a border wall, acknowledged he had warned Democrat leaders that an impasse could last for months or even years if a deal cannot be reached on financing for the wall.

Contributing: Kevin Johnson, USA TODAY