SAN FRANCISCO — A top executive and daughter of the founder of the Chinese tech giant Huawei was arrested on Saturday in Canada at the request of the United States, in a move likely to escalate tensions between the two countries at a delicate moment.

The arrest of Meng Wanzhou, the chief financial officer, unfolded on the same night that President Trump and President Xi Jinping of China dined together in Buenos Aires and agreed to a 90-day trade truce. The two countries are set to begin tense negotiations in hopes of ending a trade war that has been pummeling both economies.

Those talks now face an even steeper challenge. The aim will be for the United States to ease its tariffs; in exchange, China will be expected to lower trade barriers and further open its markets to American businesses.

What’s more, Ms. Meng’s detention raises questions about the Trump administration’s overall China strategy. Beijing is now likely to pressure Canada to release her and to press the United States to avoid a trial.