Waterloo, Iowa(CNN) Chicago Mayor Lori Lightfoot pressed presidential hopeful Pete Buttigieg to break his non-disclosure agreement with the elite consulting firm that once employed him, as the crowded 2020 Democratic race progresses toward the Iowa caucuses.

Lightfoot asked the South Bend, Indiana, mayor, "Shouldn't you break that NDA (with McKinsey and Company), so that you have the moral authority and the high ground against somebody like (President Donald) Trump, who hides behind the lack of transparency to justify everything he's doing?"

Buttigieg, who was being interviewed by Lightfoot on Friday as part of a forum hosted by the US Conference of Mayors and Accelerator for America in Waterloo, Iowa, pointed to a newly released statement from his campaign that detailed the projects, though not the clients, he worked with during his time at McKinsey.

The release came after some of Buttigieg's presidential opponents also called on him to be more transparent about his time at the firm as some of McKinsey's work for the federal government, including for Immigration and Customs Enforcement on projects along the US-Mexico border, drew increased scrutiny this month.

"I've pushed as much information as I can, without breaking the promise that I made in writing," Buttigieg told Lightfoot. "And I am asking my former employer to do the right thing, to not make me choose between claiming the moral high ground and going back on my word."

Lightfoot, however, seemed skeptical. "But they're not going to do that, right? And NDAs are, courts across the land have said that they're not enforceable, you should break the NDA."

For his part, Buttigieg, said, "I'm going to give them a chance to do the right thing, and then we'll take it from there."

Later, Lightfoot told reporters that while "Pete is, as you saw, a really tough smart, thoughtful guy who's taking the experience that he has as the mayor of South Bend and elevating that to what the solutions can be on a national level," she's concerned an NDA could hurt him in a general election fight against Trump.

"The fact of the matter is, it's going to be a brutal nasty general election campaign, and anybody who thinks that Donald Trump isn't going to fight hard, and in the mud on every issue is fooling themselves," Lightfoot told reporters in Iowa. "And when you've got an issue that he's going to equate to his issue, you got to figure out how to deal with it."

On the campaign trail, Buttigieg, who is a gay Midwestern mayor, often casts himself as the antithesis of Trump. In a gaggle with reporters, Lightfoot, herself an openly lesbian Midwestern mayor, joked to CNN, "I know a little bit about that," but "It's not enough, as I think any mayor here would attest, to not be Donald Trump, we've got to speak to a positive message that's going to speak to the core component of the Democratic Party, the Independents, the suburbanites, who are sick and tired of all the vitriol and the divisiveness, that's what we want, we need somebody who's not only going to speak the values, but also have a real plan to deliver, because as mayors, we can't kick the can down the road."

Lightfoot has not yet endorsed a candidate in the 2020 Democratic primary, though she told reporters in Iowa on Friday she'd likely wait until after the Iowa caucuses in February.