A top Chinese economic official appealed for cooperation during trade talks with U.S. delegates Monday in the southwestern Chinese city of Chengdu.

Chinese Vice Premier Wang Qishan warned the U.S. delegates against politicizing the negotiations.

U.S. Secretary of Commerce John Bryson warned that attitudes toward trade ties with China are worsening in Washington.

The U.S.-Chinese Joint Committee on Commerce and Trade, which meets twice a year, is aimed at resolving trade tensions by focusing on policy disputes.

Monday's meeting comes amid mounting demands by some American lawmakers for punitive tariffs on Chinese goods if Beijing fails to ease controls that keep its currency undervalued and gives its exporters an unfair trade advantage.

U.S. officials have long accused China of keeping its currency artificially low, a policy that helped send the U.S. trade deficit with China to more than $270 billion in 2010.