China Wednesday denied it is a "currency manipulator" and warned US presidential candidates not to engage in "election politics" when dealing with the world's second largest economy.

"We hope the US Republican and Democratic candidates will get rid of the impact of election politics and do more things conducive to China-US mutual trust and cooperation," Chinese foreign ministry spokesman Hong Lei told reporters Wednesday.

In the second presidential debate Tuesday night, Republican presidential nominee Mitt Romney repeated the rhetoric he has made throughout his campaign trail, saying he would declare China a "currency manipulator" once he is elected, attacking US President Barack Obama for his "soft policy" on China.

Obama fiercely pounded back by questioning the former Massachusetts Governor's record of making money by investing in Chinese companies, including ones "that are building surveillance equipment for China to spy on its own folks."

"Governor, you're the last person who's going to get tough on China," Obama said.

Romney did not shy away from the issue of his own foreign investments. He then challenged the president. "Have you looked at your pension?" he said, adding that Obama also has investments in China.

"The fact that both candidates are investing in Chinese companies demonstrates that close trade ties between China and the US serve the interests of both countries," Niu Xinchun, a US studies expert at the China Institute of Contemporary International Relations, told the Global Times.

Obama sought to portray himself as the leader that knows best how to deal with China's trade policy, suggesting that the Chinese currency has gone up 11 percent in value since he has been president.

Niu said the Obama comments are baseless. "The Chinese currency is adjusted according to the demand of China's economic development and it will not be decided according to pressure from any other countries."

The Obama administration has recently taken protective measures against Chinese commodities exported to the US, including pushing for tariffs on Chinese-made solar panels and tires, a move that Beijing slammed as "unfair."

"Both Obama and Romney want to score political points by attacking China. But I don't think they will really follow through on some of their campaign rhetoric if they are elected," Niu said.

In his 2008 presidential campaign Obama also promised to label China a currency manipulator.

In the town-hall-style debate held at Hofstra University in New York just three weeks before election day, Obama and Romney also traded blows over economic policy.

"The middle class is getting crushed under the policies of a president who has not understood what it takes to get the economy working again," Romney said.

Obama responded sharply, chiding Romney for his low personal income tax rate and his infamous comment about the "47 percent" of voters dependent on the government.

Agencies contributed to this story