Treasury Secretary Steven Mnuchin on Thursday said the administration is committed to ensuring that the middle class doesn't pay more under tax reform but added that he can't "make any guarantees."

"I can't make any guarantees until this thing is done and on the president's desk," Mnuchin said during an interview on ABC's "Good Morning America." "But I can tell you, that's our No. 1 objective in this."

The details of taxes are "very complicated," he said, adding that the administration is "committed to working quickly and getting this done."

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"Let me just say, this isn’t about President Trump’s tax returns; this is about the American public’s tax returns," Mnuchin said. "This is about creating economic effect for small- and medium-sized businesses and making sure they have the same opportunities as large corporations."

The Trump administration on Thursday unveiled a sweeping tax reform plan that would create three tax brackets for individuals. Most itemized deductions would be eliminated, including the deductions for state and local taxes, but not deductions for mortgage interest and investment. The standard deduction would be doubled.

The tax rate for corporations and most businesses would be reduced to 15 percent.

"We're tired of in this country having the highest business tax rates, taxing on worldwide income and leaving trillions of dollars offshore," Mnuchin said.

"It's not a surprise that American business has left trillion dollars offshore. This is about bringing back that money. ... This is about getting the most sweeping tax cuts and tax reform passed by this president to create economic growth."

The White House provided a one-page summary of its plan that is short on details. The proposal is already raising GOP concerns about blowing up the deficit.