Steven Mnuchin, the Treasury secretary, listening as President Trump addressed top business executives during a meeting at the White House on Tuesday.

Steven Mnuchin, the Treasury secretary, may have spent the last week focused on trying to combat terrorist financing in the Middle East, but overhauling the tax code was never far from his mind.

As his military aircraft cruised through the sky on Monday night from Doha to Washington, Mr. Mnuchin juggled completing an agreement with the Qataris in between calls with the House Ways and Means Committee chairman to put the finishing touches on the Republican tax plan. In a brief interview, he also shared his latest thinking on the status of the tax overhaul, financial regulation and life in the spotlight.

“It’s a big week and I’ve been on the phone multiple times a day, sometimes in the middle of the night,” Mr. Mnuchin said of his discussions on the tax plan while traveling in Saudi Arabia, Israel, the United Arab Emirates and Qatar. “We’re almost there.”

Here are some highlights from the interview.

Mr. Mnuchin dismissed criticism that the Republican tax plan was for the rich, insisting that the bill would ultimately benefit the middle class the most.

He contended that the tax models used by the Joint Committee on Taxation should not be the only ones to assess the plan, and he said he sided with economists who believed that cuts to corporate taxes would benefit workers more than shareholders.

“When you do distribution tables, you take a bunch of things like the corporate tax and you distribute them out,” Mr. Mnuchin said, explaining that the lower rate for businesses should be viewed in conjunction with lower individual tax rates. “We’re focused on what does this mean to the middle income in terms of tax cuts.”

Mr. Mnuchin defended his department’s decision to remove a study from its website that…