Answer:
the United States began passing economic sanctions against Japan, including trade embargoes on aircraft exports, oil and scrap metal, among other key goods, and gave economic support to Guomindang forces. In September 1940, Japan signed the Tripartite Pact with Germany and Italy, the two fascist regimes then at war with the Allies.
Tokyo and Washington negotiated for months leading up to the Pearl Harbor attack, without success. While the United States hoped embargoes on oil and other key goods would lead Japan would halt its expansionism, the sanctions and other penalties actually convinced Japan to stand its ground, and stirred up the anger of its people against continued Western interference in Asian affairs.
