Einstein's writings (illustration)
Einstein's writings (illustration) Albert Einstein archives, Hebrew University

Albert Einstein quietly fumed at the US for not doing more to stop the Nazis, a letter being auctioned later this month reveals. 

"You can imagine how the new crimes committed by the Nazis in France make me suffer, crimes assisted to by the 'fascist' Vichy-traitors," Einstein wrote, in a letter dated September 3, 1942. The letter was published in full Thursday by the Daily Mail.

He hesitated to approach Washington on the issue, however - saying the US government was "a government controlled to a large degree by financiers the mentality of whom is near to the fascist frame of mind." He further raged against the US's support of Spanish dictator Francisco Franco.

Einstein lamented that his views put him in a difficult position, as he was "grateful having found and sought refuge and protection" from the Nazi regime in the US, and yet he wielded a great deal of influence, being considered one of the most important Americans at that time. While he believed that the US could be doing more to stop Nazi Germany, he ultimately declined from making his views public. 

"If Hitler were not a lunatic he could easily have avoided the hostility of the Western powers," he added. "That he is a lunatic is the sole advantage in the present sinister picture of the world." 

Einstein addressed the letter - which has never been revealed to the public until now - to Dr Frank Kingdon, President of Princeton University, who shared the Jewish scientist's concerns. 

The letter will go up for auction, to the tune of £30,000 ($42,246), on April 18.