The United States can't lead the world in the 21st century with its current energy policy, Vice President Joe Biden told alternative technology supporters Tuesday at a clean energy summit in Las Vegas.

The nation is already trailing China and Germany in green technology, Biden said. It will trade its dependence on foreign oil for a dependence on foreign clean energy technology if its leaders don't act to help fledging green researchers and businesses, he said.

"If we shrink from deciding whether we are going to lead in the area of alternative energy, renewable energy, then we will be making the biggest mistake that this nation has made in its history," Biden said during his keynote speech at the fourth-annual National Clean Energy Summit at the Aria hotel-casino.