While I don't know for certain, it should be remembered that World War II began in Europe on 1 September, 1939 and it wasn't until 7 December, 1941 that the United States entered the war as a full belligerent. While Congress had outlawed the selling of arms to the opposing sides in a war with the Neutrality Acts of 1935 and 1937, the ironically named Neutrality Act of 1939 overturned the ban on the sale of arms through the 'Cash-and-Carry' policy (no purchase on credit) and later, in March, 1941, through the 'Lend-Lease' policy.
But, so far as I know (I could be wrong), there were no restrictions on the sale of goods other than weapons to any of the nations fighting in the war. As such, it certainly would not be surprising that private U.S. owned firms, including oil companies, would have continued to do business with the Third Reich prior to the bombing of Pearl Harbor if there was a profit to be made. Certainly, during the Spanish Civil War, U.S. oil companies provided the Nationalists under Franco with fuel for their war machine.
That being said, doing business with the Third Reich would have presented some difficulties for U.S. firms. Reprising their role in the First World War, Britain's Royal navy made a point of ensuring that no merchant ships headed for Germany entered the Baltic Sea (those headed for neutral Sweden were probably regulated in the same manner that shipping headed for neutrals in World War I were controlled by the Royal Navy).
Lastly, it's more than a little 'cheeky', as the British would say, for a Russian to complain about the U.S. engaging in trade with the Third Reich before its entry in the war, given that, right up until the Wehrmacht launched its invasion of the U.S.S.R. on 22 June, 1941, train loads of raw materials were crossing into Germany to supply Hitler's war machine. Through the Molotov-Ribbentrop Pact of 23 August, 1939, and, in February, 1940, an expanded trade pact, Stalin promised - a promise he largely fulfilled - to supply Germany with vast quantities of raw materials, including 900,000 of oil, enabling Hitler to weather the British naval blockade.