Updated at 6:30 p.m. with comment from Texas Rep. Mike Conaway.

WASHINGTON — A House Armed Services Committee hearing for Secretary of Defense nominee Gen. James Mattis was canceled Wednesday, a day before his scheduled appearance.

The U.S. Marine Corps veteran was expected to speak before the committee led by Texas Rep. Mac Thornberry on Thursday about whether he should be granted an exemption to a law barring military members on active duty in the past seven years from heading the Pentagon. Mattis retired from the military in 2013.

Texas Rep. Mike Conaway, a member of the Armed Services Committee, said the appearance was canceled by President-elect Donald Trump's transition team. Mattis' testimony was scheduled the same day as his confirmation hearings before the Senate Armed Services Committee.

"Mattis was willing and able to come and visit with us, but the transition team didn’t want that to happen and so it’s not going to happen,” said Conaway, a Republican from Midland. “He would’ve done well. He might’ve helped us get more Democrats on board for the vote, but nonetheless, we’ll pass it.”

The Trump transition team did not respond to a request for comment by deadline.

The long-serving general, nominated by Trump last month, does not need to appear before the House committee for Congress to vote on the legal exemption, or waiver.

But before he can be confirmed by the Senate, the House must grant the exemption, giving that chamber a rare opportunity to weigh in on Cabinet appointments. The 1947 National Security Act is designed to buttress civilian oversight of the military.

Some Democrats, including Texas Rep. Joaquin Castro, D-San Antonio, slammed Mattis' cancellation on Wednesday.

"General Mattis should not get a waiver if he refuses to testify before the House of Representatives," Castro, a former member of the Armed Services Committee, said in a tweet.

General Mattis should not get a waiver if he refuses to testify before the House of Representatives. — Joaquin Castro (@JoaquinCastrotx) January 12, 2017

In testimony before the Senate Armed Services Committee on Tuesday, national security experts encouraged senators to approve the waiver, while cautioning against setting a precedent for retired generals to run the Pentagon, The Washingon Post reports.

On Thursday, the House committee will still meet to consider the legislation to grant the waiver, Conaway said, which is expected to sail through the Republican-controlled House. But the measure could face a tougher hurdle in the Senate, where GOP members hold a narrow majority.

With the exception of Supreme Court nominations, presidential appointments require a simple majority. But Republicans need to overcome a 60-vote threshold to change the law for Mattis.

The decision to cancel the hearing comes amid reports that U.S. intelligence chiefs briefed President Barack Obama and Trump last week on allegations that Russian spies have "compromising personal and financial information" about the incoming president.

Last December, Sen. Kirsten Gillibrand, D-N.Y., was among the first to announce she'll oppose granting him the legal exception. But Thornberry, the Republican from Clarendon, has said he'll push for his approval in the House.

Mattis' hearings are among several scheduled on the Hill this week, including for Alabama Sen. Jeff Sessions for attorney general and Exxon Mobil chief Rex Tillerson for the State Department.