Vietnam was the retail industry's backup plan when Trump first imposed duties on China, so some executives are relieved to see a potential deal with 20% levies.

SINGAPORE—A tariff agreement with Vietnam emphasizes one of the White House’s top priorities in this frantic round of dealmaking over global trade: Slamming shut any back door routes for Chinese goods to enter the U.

The Trump administration’s new trade deal with Vietnam aims to shut down any “backdoor” routes that allow Chinese goods to