As the Senate prepares to vote on the new United States-Mexico-Canada Agreement (USMCA), Democratic presidential candidates debated whether it was an improvement to the current trade situation and worth supporting.

Billionaire Tom Steyer — who has made climate issues a centerpiece of his campaign — blasted former South Bend, Ind., Mayor Pete Buttigieg for supporting the USMCA without ensuring it has provisions to deal with climate change.

“If climate’s your number one priority, you can’t sign a deal — even if it’s marginally better for working people — until climate is also taken into consideration. Look, I’ve four kids between the ages of 26 and 39. I cannot allow this country to go down the path of climate destruction. Everybody in their generation knows that.”

Watch his comments below:

.@TomSteyer accuses @PeteButtigieg of putting climate on the "backseat" #DemDebate pic.twitter.com/G0s6Wsyzcj

— Washington Examiner (@dcexaminer) January 15, 2020

“Franky, Mayor Buttigieg, you’re their generation. I think you would be standing up more. Look, that’s what I’m standing up for. We cannot put climate on the backseat all the time, and say, ‘We’re going to sign this one more deal. We’re going to do one more thing,’ without putting climate first.”

“That’s right,” Buttigieg agreed. “That’s why we’re going to tackle climate from day one. It’s why we’ve got to make sure that we have got better answers than we do today.”

“Now what I’ve noticed is, pretty much all of us propose that we move on from fossil fuels by the middle of the century — starting with actions we take right now. The question is: How are we going to make sure any of this actually gets done? Because people have been saying the right things in these debates for literally decades.”

Watch his response below:

Future generations will sit in judgment on whether we actually put together the national project necessary to take on climate change and move our country to a better place. #DemDebate pic.twitter.com/nESG8Dbg60

— Pete Buttigieg (@PeteButtigieg) January 15, 2020

Steyer has hit Buttigieg for not making climate issues a more significant part of his campaign before, especially given his age.

“You’re 37 years old. You know, you’re of a generation of people who understand this is the number one issue in front of us,” Steyer said in December, adding, “‘Why aren’t you stronger on climate?’ That, to me, is an absolutely critical question for him to answer.”