WASHINGTON (AP) — The United States and China have taken pains this week to emphasize that their trade talks are entirely separate from the U.S. case against a top Chinese technology executive. But with a few words, President Donald Trump obliterated the distinction, saying he'd wade into the case if it would help produce a trade agreement with China.

China has already detained a former Canadian diplomat in what appears to be retaliation for Canada's arrest of Meng Wanzhou, the chief financial officer of telecommunications giant Huawei. On Wednesday, Canadian Foreign Minister Chrystia Freeland...