Mattis, a retired Marine Corps general tapped by President-elect Donald Trump to oversee the Pentagon, is scheduled to testify at his Senate confirmation hearing Thursday morning. But he was also scheduled to head across Capitol Hill and talk to House members later in the day, an unusual but not unprecedented appearance before both chambers.

On Wednesday, officials from Trump’s transition team told committee staff Mattis would not attend the second hearing, without further explanation.

The cancellation complicates an already unusual nomination process for Mattis, a popular figure in military circles and on Capitol Hill…

Following the cancellation news, House Minority Whip Steny Hoyer, D-Md., said Democrats in his chamber may oppose the waiver if Mattis doesn’t testify before their lawmakers to answer questions about his views on civilian control of the military.