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(CNN) —  

House Democrats are fuming after Ret. Gen. James Mattis abruptly canceled his appearance before the House Armed Services Committee slated for Thursday. The move is triggering a backlash from top House Democrats who say without hearing directly from Mattis they will oppose legislation paving the way for his confirmation.

“The Republicans have been spending eight years complaining about the executive branch usurping legislative branch power and here’s their first move from the new administration is to ignore us on something,” Rep. Adam Smith, D-Washington, the top Democrat on the panel told reporters Wednesday.

Smith added, “This is a law. We have to pass it and we want to hear from him and if we don’t we are going to vote no.”

Current law prohibits anyone who has served in the military in the last seven years to have a top leadership position in the Pentagon. That means Congress needs to pass a law that provides an exception for Mattis, who retired three years ago, to serve as defense secretary before the Senate votes on his confirmation.

Smith told reporters that Trump transition officials made the decision to pull Mattis from the House hearing Wednesday. Mattis did initially agree to House Armed Services Chairman Mac Thornberry’s request to appear and answer questions from members about taking a job typically held by civilians.

“General Mattis’ current focus is on following the constitutional process for confirmation by the United States Senate and testifying at his confirmation hearing of the Senate Armed Services Committee, if confirmed he looks forward to working with both the Senate and House Armed Services Committees, which play critical roles in supporting our forces and ensuring civilian control of the military,” said Alleigh Marre, a Trump transition spokeswoman.

House Republican leaders scheduled a vote for Friday on a bill to provide Mattis with a waiver, and even with potentially large numbers of Democratic defections GOP aides say they are confident the measure will pass.

Thornberry is expected to support the bill, according to an aide, despite the dust-up on the hearing.

Mattis already had a busy day slated for Thursday, when he will testify at his confirmation hearing before the Senate Armed Services Committee. That panel is also expected to approve the Mattis waiver bill later in the day.

Since he was tapped by President-elect Donald Trump to lead the Pentagon Mattis has received bipartisan praise for his military career. While some have expressed concerns about setting aside the precedent of maintaining civilian leadership in the military, it’s expected that the waiver legislation will be approved by both chambers and Mattis will be confirmed as one of the first Cabinet members. Senate leaders are aiming to have his confirmation vote on Inauguration Day, January 20.

CNN’s Ryan Browne and Ted Barrett contributed to this report