U.S. President Barack Obama on Wednesday called for a "new era of energy exploration in America," saying that the United States must lead the world on renewable energy.

"On this Earth Day, It is time for us to lay a new foundation for economic growth by beginning a new era of energy exploration in America," Obama told workers at a wind power technology plant in Iowa, the state that launched him toward the White House.

"The nation that leads the world in creating new sources of clean energy will be the nation that leads the 21st century global economy," said the president, "America can be that nation. America must be that nation."

Obama also unveiled a program to develop the renewable energy projects on the waters of U.S. outer continental shelf that produce electricity from wind, wave, and ocean currents.

The Interior Department on Wednesday issued long-awaited regulations governing the development of offshore wind and tides, which will enable, for the first time ever, the United States to tap into its ocean's vast sustainable resources to generate clean energy in an environmentally sound and safe manner.

Obama said that wind could generate as much as 20 percent of the U.S. electricity demand by 2030 if its full potential is pursued on land and offshore. It would also create as many as 250,000 jobs, he said.

"As with so many clean energy investments, it's win-win: good for environment and great for our economy," the president said.

According to the American Wind Energy Association, wind-produced electricity totals just under 2 percent of all electricity generated in the United States.

In Landover, Maryland, Vice President Joe Biden marked Earth Day by announcing that 300 million U.S. dollars in federal stimulus money will go to cities and towns to purchase more fuel-efficient vehicles.

"For city and state governments across this country, every day is Earth Day thanks to the ambitious commitments they are making to green their vehicles and transit systems. Now it's time for Washington to help them deliver on those promises," said Biden.

More than a billion people around the world were expected to take part in the 40th anniversary Earth Day events, designed to highlight how an educated global population can preserve its environment.