MANILA, July 11 (Reuters) - Copper and zinc prices slumped to their weakest in about a year while other metals also sank in a broad selloff on Wednesday after the United States raised the stakes in a trade war with China with threats of more tariffs. The Trump administration said it would slap 10 percent tariffs on another $200 billion worth of Chinese imports, raising fears the festering trade dispute between the world's two biggest economies could hit global growth. "There certainly is going to be pronounced risks mainly because we've now moved on to the tit-for-tat-for-tit phase of it," said Vishnu Varathan, head of economics and strategy at Mizuho Bank in Singapore. Last week, Washington imposed 25 percent tariffs on $34 billion of Chinese imports and Beijing responded immediately with matching tariffs on the same amount of U.S. exports to China. "This is going to drag on until they can all come to the table and agree to even the playing field. But the unpredictability of the situation continues to rattle the markets," said Varathan. Three-month copper on the London Metal Exchange dropped as much as 3.8 percent to $6,092.50 a tonne, its lowest since July 25 last year. It was down 3 percent at $6,140 by 0323 GMT. On the Shanghai Futures Exchange, the most-traded copper fell as far as 47,800 yuan ($7,175) a tonne, its weakest since June 23 last year. Zinc was also hard hit, with the metal dropping by its 6 percent downside limit in Shanghai to 20,620 yuan per tonne, the lowest since June 22 last year. It fell as much as 4.8 percent to $2,503 in London, the lowest since June 15, 2017. * U.S. TARIFFS: U.S. officials released a list on Tuesday of thousands of Chinese imports the Trump administration wants to hit with the tariffs, including hundreds of food products as well as tobacco, chemicals, coal, steel and aluminium. * CHINA RESPONSE: China's assistant commerce minister said on Wednesday that the latest proposed tariffs from the United States harms the World Trade Organization system and hurts globalization. * MARKETS: China's shares tumbled and the dollar rose to near an 11-month high against the yuan while the Australian dollar dropped along with other Asian equities. * OTHER METALS: Other metals also slid to multi-month lows before paring some losses, with LME nickel down 3 percent and lead down 2.6 percent. In Shanghai, nickel and lead fell more than 2 percent.