China struck back at President Trump on Friday, imposing 34 percent tariffs on all U.S. products, matching the levies that he announced this week on Chinese goods. Stock markets plunged further as worries deepened about a global trade war. The Stoxx Europe 600 index fell more than 4 percent, erasing its gains for the year and extending the slide in global markets that began Thursday after Mr. Trump announced steep worldwide tariffs. In Japan, the Nikkei 225 fell 2.8 percent, matching its drop the day before. The S&P 500, which posted its worst daily loss since 2020 on Thursday, falling 4.8 percent, was set to fall about 3.5 percent on Friday, according to futures trading. The dour market news came hours before the latest official snapshot of the U.S. labor market was set to be released, which analysts and policymakers were watching for the impact of the Trump administration’s economic policies.