I think it was US that imposed sanctions on Japan first.
AI Overview
The United States imposed economic sanctions on Japan during World War II to stop Japanese aggression. These sanctions included freezing Japanese assets in the United States and a ban on oil exports to Japan.
Sanctions
Freezing Japanese assets: The United States froze Japanese assets in U.S. banks. This made it difficult for Japan to buy American oil.
Oil embargo: The United States banned oil exports to Japan, including aviation fuel and motor fuel for airplanes.
Scrap metal embargo: The United States embargoed the export of scrap metal to Japan.