Joe Biden said he would not ban the practice of fracking for natural gas, distancing himself from some of his Democratic rivals, but said he would evaluate existing fracking permits to determine their safety.

“We can pass national legislation, but I don’t think we would get it done to say all fracking going on ends unless we can say there is some physical security need,” Biden said Wednesday night at CNN’s climate change town hall, in response to a question about banning fracking.