Presumptive Democrat nominee Joe Biden Friday doubled down on promises to stop the Keystone XL pipeline, but insisted that he does not want to stop all gas and oil projects immediately. 

"I've been against Keystone from the beginning. It is tar sands that we don't need — that in fact is a very, very high pollutant," Biden said Friday on CNBC's "Squawk Box."

Tar sands, also called oil sands, are a mixture of clay, water, sand and bitumen, a thick black oil that is refined and mixed with lighter oils, according to the American Geosciences Institute.   The process for removing the oil is condemned by environmentalists because it depends on using large amounts of land for open-pit mining, water, and energy. 

Biden on Friday dismissed the importance of the Keystone project to the oil industry, When pressed by an interviewer about the damage this pledge might do to the oil industry, Biden replied that he doesn't want to shut down all projects immediately.

"We're going to transition gradually to get to a clean economy," said Biden. "The idea of shutting down Keystone as if that is the thing that keeps the oil industry moving is just not rational."

Further, stopping fracking does not "economically make any sense," Biden said, but he would still move away from the practice used to extract oil from the ground. 

"I would not do more fracking on federal lands," said Biden. "I would gradually move us out of the position of relying on oil and gas and coal. No one's going to build another coal-fired plant, period, no matter what the law is because now you can build a renewable energy or you can build a natural gas plant that works better and is cheaper and can have fewer problems."

A rational policy on global warming, meanwhile, will also help create millions of jobs, said Biden. 

• Trump Administration Approves Keystone Pipeline on US Land
• Keystone Pipeline Opponents Ask Judge to Strike Down Trump's Permit