NEWTON, Iowa (Reuters) - President Barack Obama said on Wednesday the United States must lead the world on renewable energy and pressed Congress to set greenhouse gas limits deemed crucial for the success of global talks on climate change.

Obama, who has kept energy reform high on his priority list since taking office in January, used Earth Day to tout the need for a U.S. shift to less-polluting fuels and a concerted effort to reduce the nation's dependence on foreign oil.

"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 propelled his presidential campaign more than a year ago.

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

U.S. negotiators are preparing proposals for international climate talks to be held in Copenhagen in December, aimed at agreeing a pact to succeed the Kyoto Protocol, which sets limits on greenhouse gas emissions.