House Oversight and Accountability Committee Chair James Comer (R-Ky.) on Wednesday issued a subpoena to secure Secret Service Director Kimberly Cheatle’s already agreed-upon appearance at a hearing set for Monday.

The Oversight panel had announced earlier in the week that Cheatle committed to appearing at the planned July 22 hearing as part of the panel’s investigation into the attempted assassination of former President Trump. But tensions have increased in recent days between House Republicans and the Secret Service and the Department of Homeland Security (DHS), and Comer said that the subpoena is necessary to ensure that Cheatle keeps her commitment to appear.

“Initially, the Secret Service committed to your attendance. Subsequently, however, DHS officials appear to have intervened and your attendance is now in question,” Comer said in a letter to Cheatle.

“In addition, since DHS’s intervention, there have been no meaningful updates or information shared with the Committee,” Comer continued. “The lack of transparency and failure to cooperate with the Committee on this pressing matter by both DHS and the Secret Service further calls into question your ability to lead the Secret Service and necessitates the attached subpoena compelling your appearance before the Oversight Committee.”

The Secret Service and DHS did not immediately respond to a request for comment. 

In response to a separate request Tuesday about a hearing invitation from another committee, a DHS spokesperson said that the department “responds to congressional requests directly via official channels, and the Department will continue to respond appropriately to Congressional oversight.”

In a statement Monday, Cheatle said that the Secret Service will “work with the appropriate Congressional committees on any oversight action.”

Speaker Mike Johnson (R-La.) earlier on Wednesday called for Cheatle to resign in the wake of the shooting and expressed concern about whether Cheatle would appear at the Monday hearing.

“We’re hearing rumblings this morning that [DHS Secretary Alejandro Mayorkas] may not allow her to attend” the hearings, Johnson said on Fox News.

Cheatle told ABC News in an interview this week that she would not step down.

Johnson also said he will create a bipartisan “task force” to streamline investigations into the shooting at the Saturday rally that resulted in a 20-year-old gunman injuring the president, killing one attendee, and leaving two others in critical condition.

An Oversight Committee spokesperson on Tuesday accused DHS of “unprofessionalism” in the wake of a scheduled Secret Service briefing that later fell apart after alleged interference from the parent department.

However, the Department of Justice and Department of Homeland Security were scheduled to host a briefing Wednesday afternoon for all House members on the attempted assassination, according to a source, with presenters including Secret Service Deputy Director Ronald Rowe and FBI Deputy Director Paul Abbate.