President Trump on Monday issued a new ultimatum to China: Rescind its retaliatory tariffs, or face a 104 percent tax on its exports to the United States starting later this week.

The president’s threat risked another major escalation in what has already become a costly and damaging global trade war, one that has roiled financial markets as countries around the world scramble to calibrate a response to Washington.

After Mr. Trump announced last week that he would impose a new 34 percent tariff on China, Beijing responded in force, threatening to impose a 34 percent tax on U.S. imports.

In response, Mr. Trump said Monday in a post on Truth Social that the United States would “impose ADDITIONAL Tariffs on China of 50%, effective April 9th.” White House officials later clarified that the tariff would be additive, potentially bringing the total taxes that Mr. Trump has imposed on Chinese imports since he came into office to 104 percent.

Those levies would come in addition to tariffs Mr. Trump placed on many products from China in his first term, along with tariffs that apply to individual products because of specific trade violations.

The escalation could result in a huge surcharge for importers bringing clothing, cellphones, chemicals and machinery in from China, which may see the cost of their imports double. American consumers last year bought $440 billion of goods from China, the second-largest source of U.S. imports after Mexico.

The president also threatened that talks with China “will be terminated!” if Beijing did not back down from its pledge to retaliate.

In making that threat, Mr. Trump appeared to issue a stark warning to nations around the world that he would issue punishing additional tariffs if U.S. trading partners tried to rebuff his policies. His comments carried particular urgency on a day that officials in the European Union planned to circulate a list of U.S. products that they could soon subject to tariffs.

Mr. Trump explicitly referred to his earlier threat that “any country that Retaliates against the U.S.” would be “immediately met with new and substantially higher Tariffs, over and above those initially set.” But he also said negotiations would begin with “other countries” starting immediately.

Jeanna Smialek contributed reporting.