Nobody expects Vietnam to replace China as the world's major exporter, but the Southeast Asian country certainly appears to be taking some of China's business with the United States.

In the first nine months of this year, U.S. imports from Vietnam jumped 34.8% year on year, accelerating from a 5.8% gain in all of 2018, according to a Thursday note by consultancy IHS Markit. In comparison, U.S. imports from mainland China shrank 13.4% year on year in the January-to-September period, the note said.

Tariffs were a major reason behind the decline in U.S. imports from China, said Michael Ryan, IHS Markit's associate director of comparative industry service, who wrote the note.

He added that Vietnam's fastest growing export categories to the U.S. are computers, telephone equipment and other machinery.

Those products were among the U.S.'s top imports from mainland China, Mongolia and Taiwan in 2018, according to the United States Trade Representative. That suggests that Vietnamese exports of those goods to the U.S. may have replaced the reduction in flows between China and America.