WASHINGTON, Jan 11 (Reuters) - U.S. President-elect Donald Trump's team has canceled a crucial appearance before Congress by his nominee to become secretary of defense, retired General James Mattis, even though Mattis himself had agreed to appear, congressional officials say.
The U.S. House of Representatives had been due to hear Mattis testify on Thursday as Congress weighs whether to waive existing law in order to allow Mattis to take the Pentagon's top job.
Because he retired from the Marine Corps only in 2013, Mattis is technically ineligible to be defense secretary since he has not been a civilian for at least seven years. That means Congress would need to grant a waiver - something it has not done since 1950.
House Democratic Whip Steny Hoyer said it was his understanding that the Trump transition team had blocked Mattis from testifying. Congressional aides also confirmed that Mattis had agreed to testify but the appearance had been blocked.
The Trump transition team did not immediately respond to a request for comment.
It was not clear whether the decision could be part of an effort to keep the focus on Mattis' confirmation hearing in the Senate, which is scheduled for earlier on Thursday.
"This (waiver) is not a minor issue. This is a major issue affecting the principle of civilian control of the military, and Ranking Member (Representative Adam) Smith believes deeply that General Mattis should come speak with the members about it," said Barron Youngsmith, a spokesman for Democrats on the House Armed Services Committee.
Still, Hoyer was upbeat about Mattis himself, saying he might be the best of the nominees for top administration positions put forward by the Republican Trump, who takes office on Jan. 20.
Republicans control the Senate, and so Mattis is expected to be confirmed in the post, if he receives the appropriate waiver. The Senate and House must both agree to exempt him from a law written when the Department of Defense was created to ensure that the U.S. military is under civilian command.
Senators expressed little opposition to Mattis' appointment at a Senate Armed Services Committee hearing on civilian control of the military on Tuesday, as the panel considered whether to issue the waiver. Outside experts, not Mattis, testified.
Senator John McCain, the Senate panel's chairman, said he would "fully support" the waiver legislation, which is expected to pass Congress.
Mattis, 66, has been warmly received by senior defense figures among both Republicans and Democrats, who believe he will adhere to core alliances and principles, even ones challenged by Trump during his election campaign. (Reporting by Patricia Zengerle, Richard Cowan and Phil Stewart; Editing by Frances Kerry)