Former Vice President Joe Biden hit back Wednesday at a campaign ad from former New York City Mayor Michael Bloomberg highlighting Biden's previous praise of his fellow Democratic presidential candidate.

"The best way to predict the future is to create it. I don't know anybody I've worked with in my career, and I've been hanging around a long time, who does more to create the future than you, Mike," Biden says in the clip shown in the Bloomberg ad.

"Mike Bloomberg transformed the city of New York into a global leader on public health and environmental stewardship. Mike Bloomberg transformed the city of New York into a global leader on public health and environmental stewardship. While others talked about climate change, Mike took action," he continues.

In a tweet accompanying the video, Bloomberg's campaign said, "Joe Biden has dedicated his life to this country. As a senator, and as a vice president, he has always stood by the side of great men. We are honored to have Joe's support."

"I don't endorse Republicans," Biden tweeted in response on Wednesday. Bloomberg won his first term as mayor running as a Republican in New York and spoke at the 2004 Republican National Convention, later switching his affiliation to independent.

The back and forth comes ahead of Wednesday evening's Democratic debate in Nevada, the first where the former mayor has qualified to take the stage.

Numerous candidates have taken aim at Bloomberg as he gains steam in the polls, with Sens. Elizabeth Warren (D-Mass.) and Bernie Sanders (I-Vt.) accusing him of trying to buy the election and billionaire Tom Steyer highlighting his support for stop-and-frisk policing as mayor.

Biden also reportedly took issue with Bloomberg's prominent usage of former President Obama in his advertising, telling a attendees at a New York fundraiser last week that "the advertising I've seen, you'd think that Mike was Barack's vice president."