(CNN) Acting Homeland Security Secretary Kevin McAleenan informed the House Homeland Security Committee on Friday that he won't testify at a scheduled hearing next week, despite being issued a subpoena.

In a testy letter to Committee Chairman Bennie Thompson, McAleenan said he was "disappointed, and extremely surprised" to receive the subpoena

The Mississippi Democrat and the acting secretary have previously worked together cooperatively.

Thompson had issued subpoenas Thursday to McAleenan and acting National Counterterrorism Center Director Russell Travers to appear at a hearing next Wednesday on terrorist threats facing the country.

The hearing is the day before McAleenan is scheduled to leave his job.

McAleenan said he is unable to testify given his impending departure, writing that he is focused on "winding down" his tenure and "facilitating an orderly and expeditious transfer" to his successor.

In the letter, McAleenan writes that Thompson refused to limit questioning to the topic of the hearing. He also notes that the subpoena appears to have violated committee rules, as it was issued by the chairman alone and apparently without notifying his Republican committee counterpart.

Thompson responded in a statement that "the Acting Secretary's letter gets the facts wrong. To be clear, no rules were broken by the Committee and his appearance remains legally required. It seems he just doesn't want to testify. But it should be no surprise that a Trump Administration official would deliberately mislead the American public."

Anything McAleenan says at the hearing has a "shelf life of 24 hours," said a senior Homeland Security Department official, noting that the acting secretary is expected to depart the following day.

"There was no indication that they were going to move to a compulsory process," said the official. "It's not an appropriate approach."

A successor to McAleenan has yet to be named. He announced his resignation two weeks ago.

The acting secretary offered for Homeland Security Undersecretary for Intelligence and Analysis David Glawe to testify instead or to find a date for his successor to testify.

McAleenan, Travers and FBI Director Christopher Wray are listed on the committee's website as witnesses for next week's hearing.

An administration official says that separately from McAleenan's resignation, the agencies were working with the committee on the format of the hearing. The agencies wanted the hearing behind closed doors, while the committee insisted on an open threats session, according to the official.

The open hearing is expected to cover terrorist threats to the US from abroad and domestically. While the senior DHS official said the format is not the reason McAleenan decided against testifying, the official acknowledges that the committee could have a "more fulsome" discussion with the agencies if the hearing were behind closed doors.

Two areas of concern for the secretary, the official said, are possible terrorist travel "due to the situation in Syria" and possible threats from an Iranian network in the event of a conflict in the Persian Gulf.