The two senior Trump administration officials Mnuchin and Lighthizer are frequently divided on economic policy issues but shared the same opinion that the tariffs were a bad idea, CNBC reported, citing a source close to the White House.
Trump made the decision to announce the tariffs after getting "riled up" by a conservative radio program on the surge in illegal immigration, the report said.
Although Mnuchin and Lighthizer opposed Trump's idea, White House senior policy adviser Stephen Miller played a key role in promoting it, the report said, while noting that the aide has long championed fiercely hawkish views on immigration.
An increasing number of migrants from Central America have been arriving to the US border with Mexico in recent months. Trump has called the surge of arrivals a crisis and declared a national emergency in February to secure funds to build a border wall.