U.S. states have spearheaded moves to curb global warming and are not ready to pass the leadership baton to President Barack Obama, according to Reuters. Regional markets to trade air pollution credits, aimed at cutting emissions that heat the planet, could be overshadowed by a federal system Obama sees as central to his environmental policy. But states plan to proceed with their own emission control programs until the White House and Congress pass a credible federal market mechanism such as "cap-and-trade" to meet Obama's targets for greenhouse gas cuts. Ten Eastern U.S. states in January set emissions limits that get tougher over time. The program requires power companies to obtain permits to pollute and allows them to sell excess permits to companies that lag their own targets. New York is the biggest polluter in the group known as the Regional Greenhouse Gas Initiative. The state's Climate Change Director Peter Iwanowitz said he welcomed federal action as long as New York had room to be tougher and experiment.