Blockade is too strong a word, but it might as well have been. The US embargoed them, then started providing weapons, fuel and volunteers to the Chinese they were at war with, then strong armed Mexico, Venezuela, USSR, Netherlands, and the British (who were already being pissy with them) to do the same.

All major oil producers. For the later three there were threats of not helping them with their war with the Nazis if they didn't comply. For the first two there were just outright threats.