Rep. Maxine Waters, chairwoman of the House Financial Services Committee, and Treasury Secretary Steven Mnuchin squabbled at a hearing, with Mnuchin going so far as to threaten to not testify before the committee again if he was not allowed to leave.

"If you'd wish to keep me here so I don't have my important meeting, and continue to grill me, then we can do that. I will cancel my meeting and I will not be back here," Mnuchin told the California Democrat at Tuesday's faceoff. "I will be very clear, if that's the way you'd like to have this relationship."

At the hearing, Democrats questioned him about when he will respond to requests for access to President Donald Trump's tax returns. As the testimony ran past three hours, Mnuchin asked to leave to attend a meeting with a foreign dignitary and clashed with Waters. She repeated that he was free to leave and fired back when Mnuchin said she should dismiss the meeting and "take the gavel and bang it."

"Please do not instruct me as to how I am to conduct this committee," Waters said.

CEOs of seven of the largest U.S. banks are set to appear before the committee on Wednesday, including J.P. Morgan's Jamie Dimon and Goldman Sachs' David Solomon.