The only actual source I've ever seen for that Stalin quote was the fictional Stalin from the computer game Command and Conquer: Red Alert. Is this quote actually attributed to the real Stalin? Has the quote been floating around since before 1995 or so, when that game was released?
Wikiquotes has a segment on this quote.[1] It's uncertain whether Stalin said it to Truman at the Potsdam conference, or whether the quote was actually said by someone else and misattributed to Stalin, but it is certain that the game designers didn't make it up for C&C: Red Alert.