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 …