The Trump administration said Vietnam's currency practices, including "excessive foreign exchange market interventions," hurt American businesses, but that it decided not to take any punitive action.
The decision to skip penalties in a new trade dispute came days before President-elect Joe Biden is to be sworn into office, and followed opposition during a recent hearing from U.S. companies doing business in Vietnam.
The Office of the U.S. Trade Representativehad been investigating Vietnam's policies and practices related to currency valuation since October.
It was the first case in which the U.S. cited currency manipulation as a reason to investigate a trading partner under Section 301 of the Trade Act of 1974, the same legal tool the Trump administration used to impose massive tariffs on imports from China.
"Unfair acts, policies and practices that contribute to currency undervaluation harm U.S. workers and businesses, and need to be addressed," U.S. Trade Representative Robert E. Lighthizer said in a statement Friday.
The USTR added while it wasn't taking any specific action at this time, it would continue to "evaluate all available options."
The Vietnamese Embassy in Washington didn't immediately respond to a request for comment.
Imports from Vietnam have grown sharply in recent years, rising from $14.9 billion a decade ago to $66.6 billion in 2019, according to Commerce Department data.
The Southeast Asian country has been a popular destination for investments by U.S. businesses avoiding China due to growing political tensions and rising costs there.
The announcement follows a decision last month by the Treasury Department to label Vietnam and Switzerland as currency manipulators, and USTR hearings in late December where representatives of American companies expressed concerns that tariffs prompted by the investigation would harm their businesses.