US presidential hopeful Mitt Romney renewed his vow Thursday to brand China a currency manipulator as he accused incumbent Barack Obama of failing to confront \"cheating\" by Beijing. The former Massachusetts governor, who is narrowly trailing in polls less than two months before the election, has repeatedly criticized Obama over ties with the rising Asian power on issues from trade to human rights and defense. Addressing a rally in the critical state of Virginia, Romney pledged to open new markets for US goods and said: \"I also want to make sure that if a nation cheats like China has cheated, we call them on the carpet and don\'t let it continue.\" Romney said that China\'s alleged undervaluing of its currency makes its products artificially cheap, which \"drives American manufacturers and American producers out of business and kills jobs.\" \"The president\'s had the chance year after year to label China a currency manipulator, but he hasn\'t done so,\" Romney said, vowing to name the Asian giant as such on his first day in office. The Treasury Department has resisted pressure to declare China a currency manipulator, a designation that would pave the way for sanctions and, according to some analysts, could set off a trade war between the world\'s two largest economies. Treasury Secretary Timothy Geithner has preferred quiet diplomacy to nudge China to let its currency appreciate. The Obama administration, despite frequent friction with China, has hoped to preserve cooperation with Beijing on issues such as the global economy, North Korea, Iran and climate change. Asked about Romney\'s charges, US Ambassador to China Gary Locke said he would \"not engage in political debates,\" though adding that the US position \"is very clear and has been very consistent\" in urging China to reform its exchange rate. \"We know that the currency is still undervalued,\" Locke said at the Carnegie Endowment for International Peace during a visit to the US capital Washington. \"The Chinese have made substantial progress and when you factor in the rate of inflation, it has appreciated significantly. But, again, still more needs to be done,\" said Locke, a former Washington state governor from Obama\'s Democratic Party. Obama\'s campaign hit back more forcefully, pointing to Romney\'s criticism of a 2009 decision to impose punitive tariffs on Chinese-made tires. The Republican had accused Obama of protectionism on behalf of labor union allies. \"If he were serious about holding China accountable, he wouldn\'t have criticized the president for standing up to China to protect American tire workers, he wouldn\'t continue to hold investments there and he wouldn\'t have proposed a tax plan that could create hundreds of thousands of jobs overseas, including in China,\" Obama campaign spokeswoman Lis Smith said. The yuan, also known as the renminbi, has appreciated more than five percent against the dollar in the past two years as China contends with inflationary pressure. The yuan has risen some 30 percent since 2005 when China loosened its grip on the currency. Critics in the United States and other developed economies accuse China of keeping its currency deliberately low to flood the world with exports of inexpensive goods, devastating the manufacturing industry elsewhere. Romney\'s campaign has noted that Obama, as a candidate in 2007, vowed to take China \"to the mat\" over its currency. The charges on China come as foreign policy increasingly enters the presidential race, with Romney criticizing Obama\'s stance on violent protests in North Africa and the Middle East triggered by an amateurish anti-Islam film on the Internet. Romney set off a storm of criticism, including from his fellow Republicans, after he accused the Obama administration of \"sympathizing\" with protesters through a statement by the US embassy in Cairo that condemned efforts to offend Muslims. Four Americans, including the US ambassador to Libya Chris Stevens, were killed in a separate attack on the US consulate in Benghazi.