CONCORD, N.H. — Presidential hopeful Bernie Sanders pledged Friday that before Democrats start voting for their nominee he would spell out how much more high-earning Americans could expect to pay in income taxes if he wins the White House.

Sanders, a self-described democratic socialist, has made income and wealth inequality the rallying cry of his campaign and said repeatedly that the wealthy would start paying their “fair share” of taxes under a Sanders administration.

But with two months until voting begins in Iowa and New Hampshire, the Vermont senator has yet to say what he considers fair when it comes to income taxes.

Sanders was pressed here during the taping of a New Hampshire Public Radio interview about what the top marginal tax rate should be. It currently sits at 39.6 percent on income above $413,200 for single filers and $464,850 for those filing jointly.

Sanders’s questioner noted that when presented with the same query on ABC’s “This Week” in October, Sanders told host George Stephanopoulous that the top rate would be “a damned lot higher than it is right now.”

Sanders did not offer a number Friday but he said he would have one before the New Hampshire primary in early February.

“It is absolutely my view that the wealthiest people in this country should start paying their fair share of taxes,” Sanders said. “Now working on the exact numbers ain’t so easy, and that’s something we’re doing right now.”

Following the radio interview, which is scheduled for broadcast on Monday, Sanders told The Washington Post that he believes it is “fair” to expect him to put forward a tax plan before the Iowa caucuses, the first of the nominating contests, scheduled for Feb. 1.

“Honestly, we want to do it well, and it’s not such an easy thing,” Sanders said.

He declined to say whether he would seek to alter the current structure of the income tax brackets or merely change the rates that apply. (To date, the Democratic front-runner, Hillary Clinton, has offered a series of tax breaks intended to benefit the middle class but not released a plan to overhaul the income tax brackets.)

Seeking to bolster his case for change, Sanders pointed during the radio interview to a new report by the Institute of Policy Studies that found that the 20 wealthiest people in the United States now own more wealth than the bottom half of the American population combined, a total of 152 million people.

“That is grotesque, that is obscene and that has got to be dealt with,” Sanders said.

Beyond the income tax, Sanders has proposed several other measures that would impact wealthier Americans, including an increase in the estate tax paid on large inheritances and a tax on Wall Street speculation.