President Donald Trump's tax plan will amount to "the biggest tax cut" and the "largest tax reform" in US history, according to Treasury Secretary Steve Mnuchin.
Mr Mnuchin gave the description during a speech in Washington this morning.
The White House is set to release the broad outlines of President Trump's proposed overhaul later in the day.
President Trump wants cuts for individuals and businesses, even as the government struggles with mounting debt.
The president is trying to make good on promises to bring jobs and prosperity to the middle class.
The top tax rate for individuals would fall by a few percentage points, from 39.6% to the "mid-30s", according to officials.
White House senior staff have already said that the top corporate tax rate would drop from 35% to 15% under President Trump's plan.
But the Treasury Secretary declined to say there would be no absolute tax cut for the wealthy, a promise he made last year during a TV interview.
"Our objective is simplifying personal taxes," he said.
The plan will not include provisions to increase spending on infrastructure projects, one possible sweetener that could help gain congressional support.
Treasury Secretary Steve Mnuchin said at @thehill event this morning that infrastructure $$ would NOT be included in Trump's tax plan.— Melanie Zanona (@MZanona) April 26, 2017
The proposal faces a massive hurdle in that lower rates would blow a hole in the budget, possibly causing the national debt to soar by more than a trillion dollars over a decade.
Without additional revenue sources to offset the tax cuts, the broad proposal would need Democratic support to clear the required 60 votes in the Senate.
Congressional Republicans could pass changes on their own with a simple Senate majority, but that would only be temporary under Senate rules.
Mr Mnuchin said he would like the tax overhaul to be permanent, but "if we have them for 10 years, that's better than nothing".
President Trump sent his team to Capitol Hill on Tuesday evening to discuss his plan with Republican leaders.
"They went into some suggestions that are mere suggestions and we'll go from there," said GOP Sen Orrin Hatch of Utah, chairman of the Senate Finance Committee.
The White House's presentation will be "pretty broad in the principles", said Marc Short, President Trump's director of legislative affairs.
In the coming weeks, President Trump will solicit more ideas on how to improve the plan, Mr Short said. The specifics should start to come this summer.
Mr Short said the administration did not want to set a firm timeline, after demanding a quick House vote on a health care bill and watching it fail.
But he added: "I don't see this sliding into 2018."
Republicans who slammed the growing national debt under President Barack Obama have said they are open to President Trump's tax plan, even though it could add trillions of dollars to the deficit over the next decade.
Echoing the White House, Republicans argue the cuts would spur economic growth, reducing or even eliminating any drop in tax revenue.