The Trump administration is not backing away from the president’s accusations that currency devaluation is the result of manipulation and is giving China unfair trade advantages.

Treasury Secretary Steven Mnuchin, speaking to Reuters in Sao Paulo, Brazil, told Reuters that the U.S. is closely monitoring China’s currency.

“There’s no question that the weakening of the currency creates an unfair advantage for them,” Mnuchin said. “We’re going to very carefully review whether they have manipulated the currency.”

Currency devaluation can undermine the effectiveness of the Trump administration’s tariffs. Tariffs increase the price of imported products, discouraging demand for foreign-made goods and shifting demand to domestic goods. But a decline in the value of China’s currency would offset this by lowering the dollar-denominated prices of its products.