(CNN) President-elect Joe Biden's nominee for defense secretary, retired Gen. Lloyd Austin, pledged on Tuesday that he will "uphold the principle of civilian control of the military" if confirmed to the post.
The vow comes as Austin must overcome objections from some lawmakers about allowing a recently retired general to assume the top civilian post at the Pentagon. Austin would be the first African American to run the department, but to win confirmation he will first need to be granted a waiver from a law requiring a secretary to wait seven years from active-duty service before taking the job.
Biden's defense secretary pick addressed those concerns directly at a Senate Armed Services Committee hearing Tuesday afternoon, saying, "If confirmed, I will carry out the mission of the Department of Defense, always with the goal to deter war and ensure our nation's security, and I will uphold the principle of civilian control of the military, as intended."
Austin, who retired in 2016, has been reaching out to top House and Senate lawmakers who will have to agree to pass legislation to grant the waiver, something granted only twice before in history, including for James Mattis to run President Donald Trump's Pentagon in 2017.
"I understand and respect the reservations some of you have expressed about having another recently retired general at the head of the Department of Defense," he said during the hearing. "The safety and security of our democracy demands competent civilian control of our armed forces, the subordination of military power to the civil."
Austin went on to say, "I spent my entire life committed to that principle. In war and in peace I implemented the policies of civilians elected and appointed over me, leaders like Secretary (Leon) Panetta. I know that being a member of the president's Cabinet -- a political appointee -- requires a different perspective and unique duties from a career in uniform."
The hearing comes as congressional Democratic leaders are pressing for quick confirmation of Biden's Cabinet and other key administration officials. That timeline may be complicated, however, by the fact that the Senate will soon have to begin an impeachment trial after the House voted to impeach Trump in his final days in office for inciting a deadly siege on the US Capitol after a joint session had convened to affirm Biden's Electoral College victory.
Another hurdle that could slow down the confirmation process for Austin is that he will, in effect, have to win two votes: one from both chambers of Congress to grant the waiver, and another from the Senate to confirm him for the position. The House is set to vote on Thursday on the waiver.
During his Tuesday hearing, Austin pledged to fight to rid the Department of Defense of "racists and extremists."
"We also owe our people a working environment free of discrimination, hate and harassment. If confirmed, I will fight hard to stamp out sexual assault and to rid our ranks of racists and extremists."
"The job of the Department of Defense is to keep America safe from our enemies," said Austin. "But we can't do that if some of those enemies lie within our own ranks."
Austin will no longer testify before the House Armed Services Committee on Thursday, as the planned hearing "to discuss civilian control of the military" has been canceled in favor of a closed-door meeting with lawmakers, according to a panel aide.
The reason for the change, the aide told CNN on Tuesday, was that the House Armed Services Committee will not be formed for the new Congress in time.
"The committee cannot formally organize until leadership from both the majority and minority have named the full list of members. It has become clear that full committee membership will not be finalized before Thursday's scheduled hearing to discuss civilian control of the military with the Secretary-designate Lloyd Austin," committee aide Monica Matoush said Tuesday. "As such, we cannot yet convene our committee organization meeting or formally conduct committee business like a hearing. Once members have been named and the committee has been organized, we will proceed."
The closed meeting with House lawmakers could help expedite Austin's nomination but also risks alienating those who wanted to hear him testify before voting on the waiver.
Austin has told Rep. Adam Smith, a Washington state Democrat who's the chairman of the House Armed Services Committee, that he is willing to answer questions and testify publicly about the waiver to reassure lawmakers about his belief in civilian control.
Smith has consistently voiced support for Austin but also said he would like to hear him testify.