BEIJING — The Chinese government vowed Wednesday to take “firm and forceful measures” against U.S. threats to expand tariff hikes to thousands of products like fish sticks, apples and French doors as their trade dispute escalates. China gave no details but earlier threatened “comprehensive measures” if Washington took more action. That prompted fears Beijing, running out of imports for retaliation due to its lopsided trade balance with the U.S., might try to disrupt operations of American automakers, retailers and others that see China as a key market. The spiraling conflict over Chinese technology policy threatens to chill global economic growth.