Acting White House Chief of Staff Mick Mulvaney told Fox News on Sunday that he hopes to see the matter resolved this week.

The White House has been searching for the origin of the leak ever since Axios published 90 days of the president’s schedule, more than half of which was designated as free, unscheduled “executive time.” The administration has called the leak “a disgraceful breach of trust,” which does not account for “the hundreds of calls and meetings Donald Trump takes every day.”

“The President is one of the hardest workers I’ve ever seen and puts in long hours and long days nearly every day of the week all year long,” White House press secretary Sarah Sanders said at the time. “It has been noted by reporters many times that they wish he would slow down because they sometimes have trouble keeping up with him.”

Former Clinton White House staffer Paul Begala offered a non-partisan condemnation of the leak, going so far as to say it was a national security “betrayal.”

I am disconcerted as well. Set aside my strong opposition to @realDonaldTrump. As a former senior White House official, it is a betrayal of our national security to leak any POTUS’ schedule. https://t.co/nITj4hKfgE — Paul Begala (@PaulBegala) February 4, 2019

Despite “hoping to have a resolution … this week,” however, Mulvaney is not optimistic about the administration’s ability to do much about it. He believes the leak came from a career government worker rather than a Trump appointee and said, “I know from my work at the [Consumer Financial Protection Bureau], it’s nearly impossible to fire a federal worker.”