SHANGHAI, April 7 (Reuters) - China's official Xinhua news agency said on Saturday that U.S. "waywardness" in its tit-for-tat tariff exchange will only end in defeat.

China warned on Friday it was ready with a "fierce counter strike" of fresh trade measures if the United States follows through on President Donald Trump's threat to slap tariffs on an additional $100 billion of Chinese goods.

On Wednesday, China imposed $3 billion of tariffs on U.S. fruits, nuts, wine and pork, just hours after the Trump administration proposed duties on some 1,300 Chinese industrial, technology, transport and medical products.

"If the U.S. says that it will pay any price, it must be firmly attacked," said the Xinhua commentary.

Rising trade tensions between the world's two largest economies follows a U.S. finding that China was engaging in unfair trade practices in connection with intellectual property protections. China rejects the charge. (Reporting by Engen Tham Editing by Michael Perry)