Senator John McCain sought to distance himself from US President George W. Bush on Monday as he called for a mandatory limit on greenhouse gas emissions in the United States to combat climate change. Mr McCain, in a speech at a wind power company, also pledged to work with the European Union to diplomatically engage China and India, two of the world's biggest polluters, if they refuse to participate in an international agreement to slow global warming. In the prepared text of his speech, emailed to reporters on Sunday night and Monday morning, Mr McCain went so far as to call for punitive tariffs against China and India if they evaded international standards on emissions, but he omitted the threat in his delivered remarks. Aides said he had decided to soften his language because he thought he could be misinterpreted as being opposed to free trade, a central tenet of his campaign and Republican orthodoxy. But he took a shot at Mr Bush. "I will not shirk the mantle of leadership that the United States bears," Mr McCain said pointedly. "I will not permit eight long years to pass without serious action on serious challenges." In speeches on the campaign trail, Mr McCain frequently highlights the threat of climate change, but he has a mixed record on the environment in the Senate. In recent years he has pushed legislation to curb emissions that contribute to climate change, but he has missed votes on toughening fuel economy standards and has opposed tax breaks meant to encourage alternative energy. In his address on Monday, Mr McCain, the presumptive Republican presidential nominee, renewed his support for a "cap-andtrade" system in which power plants and other polluters could meet limits on heat-trapping gases like carbon dioxide by either reducing emissions on their own or buying credits from more efficient producers.