Democrat frontrunner Joe Biden (D) told a concerned activist in New Hampshire Friday that he guarantees that “we are going to end fossil fuel.”

Biden took questions from a group in New Castle, New Hampshire, Friday. One woman associated with the environmental group 350 New Hampshire Action, Rebecca Beaulieu, asked Biden how voters can trust him if he continues to associate himself with fossil fuel executives.

“How can we trust that you’re going to act on climate — on the climate crisis — if you’re still attending fundraisers that fossil fuel executives are attending?” Beaulieu asked, according to the Daily Mail.

Video shows Biden walking over to the woman, taking her hand, and making a solemn promise to “end fossil fuel … before 2050, God willing.”

“Kiddo, I want you to just take a look. I want you to look into my eyes,” Biden began.

“I guarantee you, I guarantee you, we are going to end fossil fuel, and I am not going to cooperate with them. Before 2050, God willing,” Biden continued, adding that 2030 is not a realistic goal:

No it can’t be done by 2030. No, not one single person is arguing it can be done by that. But it can be done by 2050. Maybe 2045? And is the science increases, we may be able to move more quickly. But we have to we can fundamentally change things in the next 10 years, though, so that we set a path? I promise you, I promise you. OK.

Beaulieu, 24, said she “wasn’t expecting” that kind of response from Biden and described it as “patronizing.”

“Just a little patronizing, because I want to be an adult at the table when it comes to conversations about climate, and what we’re going to do about it, and I don’t want to be like someone who’s sitting on the sidelines waiting for other people to act,” she said, according to the Daily Mail.

“I’m also like actively doing something to try to combat this climate crisis as it stands. Being called a kid is a little patronizing when I’m trying to do so much work,” she added.

She also said she was unsatisfied with Biden’s refusal to bend his 2050 goal.

“But I hope that he takes the climate crisis as seriously as he tried to make it seem and that if he’s going to keep moving forward with his plans, he needs to reevaluate because 2050 is too late,” she said.

Biden recently came under fire for attending a fundraiser hosted by Andrew Goldman, a founder of the natural gas company Western LNG. The former vice president dismissed concerns, telling viewers of CNN’s climate change town hall Wednesday that Goldman is “not a fossil fuel executive.”

“He is not a fossil fuel executive,” Biden said. “And the fact of the matter is that — what we talk about is, what are we going to do about those corporations? What have we done?”

“And everywhere along the way — for example, I’ve argued and pushed for us suing those executives who are engaged in pollution, those companies engaged in pollution,” he added. “I’ve never walked away from that.”