Treasury Secretary Steven Mnuchin got into a fiery exchange with U.S. Rep. Maxine Waters on Tuesday during a committee hearing with lawmakers on Capitol Hill.

At the end of a three-and-half-hour testimony before the House Appropriations Committee and Financial Services Committee, which is chaired by Waters, Mnuchin interrupted the hearing to remind the committee of a prior agreement that he would be able to leave by 5 p.m.

Mnuchin said that he was scheduled to meet with a senior official from the Bahrain government. After running overtime, he said he would be willing to stay until 5:15 and return at a later date to testify before Congress.

"It will be embarrassing if I keep this person waiting for a long period of time," Mnuchin said.

His departure, however, did not come without a heated back-and-forth with Waters.

"Unfortunately, we are all pressed for time," said the California congresswoman, whose committee grilled Mnuchin about his plans to respond to Democrats’ requests for access to President Trump’s tax returns.

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Waters refused to formally dismiss Mnuchin, whom she asked to stay for an additional 10 minutes, Bloomberg reported. "This is a new way and it's a new day. And it's a new chair. And I have the gavel," she said.

Mnuchin said he'd “rethink” whether he would return to sit before the committee if he was going to be poorly treated.

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

After Waters proceeded to continue with the hearing, Mnuchin again chimed in to clarify whether or not Waters was “instructing” him to stay, and therefore, cancel his meeting.

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"You made me an offer that I accepted," Waters said. "No, I'm not ordering you. I said you may leave anytime you want and you said OK.”

Mnuchin replied that he could not leave until Waters dismissed him. “You're supposed to take the gavel and bang it,” he said.

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Waters then interrupted him, saying, “Please do not instruct me as to how I am to conduct this committee."

Mnuchin was eventually advised by staff that he was not obligated to stay and could leave. Before Waters ended the hearing at 5:30 p.m., Mnuchin withdrew his offer to return before the committee in May.