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.

Vietnam on Thursday hailed as a breakthrough a long-awaited trade deal with the United States and said its negotiators were coordinating with U.S. counterparts to formalise terms with Washington,

President Donald Trump said he had reached a trade deal with Vietnam following weeks of intense diplomacy between the nations and ahead of a deadline next week that would have seen higher tariffs imposed on the country’s imports.