There was a cabinet member who agitated for the US to bomb the camps, because everyone was aware of what was going on there. Until 1945, there was no move made. Risking air crews to carry out bombing runs on targets with no military significance wouldn't have made sense from the standpoint of ending the Third Reich.
By contrast, during the Warsaw Uprising, Stalin ordered a full stop by the Red Army, to allow the Germans to snuff it out; and of course, Stalin ordered the massacre of the Polish officers, and the USSR framed the Germans for that as well. Oh, and the USSR didn't lift a finger to help the victims of the Holocaust. Raoul Wallenberg was arrested in 1944 by the Red Army in Hungary, supposedly executed by either bullet or poison in 1947, but may have been alive in the 1980s, still in custody.