President Donald Trump's economic adviser pushed back Thursday against the suggestion that the administration's tax plan could benefit the wealthy, but said he couldn't guarantee that taxes won't go up for some middle-class families.

"I can't guarantee anything," Cohn told "Good Morning America" on ABC. "You can always find a unique family somewhere."

"There's an exception to every rule," he added.

But he said the tax plan was "purely aimed" at benefiting middle-class families. Cohn said a hypothetical family of four should have "a substantial tax decrease," in the range of $650 to $1,000.

Pressed on whether Trump himself could see a tax cut under the plan, Cohn said the administration was "very confident that Americans are getting a great deal here." He added: "We have also said wealthy Americans are not getting a tax cut."

At a White House briefing later in the day, Cohn said he was sticking around in the Trump administration for the "once-in-a-lifetime" opportunity to help rewrite the nation's tax laws, adding that he would "never miss this."

Cohn had sharply denounced Trump's response to the racial violence in Charlottesville, Virginia, last month. Cohn, who is Jewish, was so upset that he considered resigning, according to news reports.

Cohn appeared with Trump when the president defended his original assessment that "both sides" were responsible for the violence and suggested that some of those who marched with the KKK and neo-Nazis were "fine people."

The blueprint released Wednesday by Trump and congressional Republicans is a sweeping, nearly $6 trillion tax cut that would deeply reduce taxes for corporations, simplify everyone's brackets and nearly double the standard deduction used by most Americans.

The president has said repeatedly that the plan would provide badly needed tax relief for the middle class. But there are many gaps in the proposal so it's hard to know how it would affect individual taxpayers and families. Still, it does include one clear benefit for the wealthy, the planned elimination of the estate tax. Under current law, the first $11 million of an estate is exempt for a married couple, meaning only the wealthiest pay it.