Treasury Secretary Steve Mnuchin can't guarantee middle class wouldn't pay more under tax plan Mnuchin said he "can't make any guarantees, but it's "our number one objective."

 -- Treasury Secretary Steve Mnuchin today told ABC News chief anchor George Stephanopoulos that he couldn’t say how Donald Trump's sweeping tax overhaul plan would affect the president personally, while also declining to guarantee that middle-class families wouldn't pay more under the proposal.

"I can't make any guarantees until this thing is done and it’s on the president's desk. But I can tell you, that’s our number one objective in this," Mnuchin said on "Good Morning America."

The blueprint, which the White House unveiled Wednesday, calls for dramatically cutting federal taxes for businesses and simplifying rules for individuals. The plan would slash corporate taxes to 15 percent for large and small businesses, as well as consolidate categories for individual taxpayers, lowering the top bracket from nearly 40 percent to 35 percent.

But the Trump administration left key questions about the tax plan unanswered, such as how it would affect the middle class and the wealthy. Mnuchin avoided sharing further details of the plan in the interview with "GMA" this morning.

"The details of taxes are very complicated and we're committed to working quickly and getting this done," the treasury secretary said.

Another "objective" of the plan, Mnuchin said, is to ensure no absolute tax cuts for the wealthy. But when pressed further by Stephanopoulos, he declined to make any guarantees on that point as well, and said he couldn't say how the plan would affect Trump himself, amid continued calls for the president to release his tax returns.

"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."

During a press briefing at the White House Wednesday, Mnuchin told reporters the president has "no intention" of releasing his tax returns.

"The president has no intention. The president has released plenty of information and I think it's given more financial disclosure than anybody else and the population has plenty of information,” Mnuchin said Wednesday when pressed at the briefing by ABC News' Jonathan Karl on whether the U.S. public has the right to know what's in Trump’s tax returns. "What this is about is creating jobs and creating economic growth."

Experts interviewed by ABC News Wednesday largely agreed that the proposed tax cuts would significantly reduce federal revenue and balloon the federal deficit. One analysis, by the bi-partisan Committee for a Responsible Federal Budget, estimates that Trump’s tax plan would cost anywhere between $3 trillion and $7 trillion in lost revenue over the next decade.

Experts also said the broad brushstrokes of the blueprint lack the necessary details on the issue's more complex and controversial questions.

ABC News' Kelly McCarthy and Ryan Struyk contributed to this report.