Hitler always planned to invade Russia, even going back to his book Mein Kamph in which he said Lebanstrom would be found in the East. He never wanted a War with Britain, he said this time and time again. Even in October 7th 1939 he said to Keitel about the Polish Territories, "It is important to us from a military point of view as an advanced jumping-off point and for strategic concentration of troops. To that end the railroads, roads and communication channels are to be kept in order." (Shirer, Rise and Fall of the Third Reich, 669) The reason why he made a Non-Aggression Pact with Stalin was to not repeat the mistakes of Wilhelm and fight a two front war. This made the German people and Italy very uneasy especially when they invaded Finland and part of Poland was parititioned to them.
Think about it, by 1941 Hitler had lost the Battle of Britain, was having minor success in Africa, and it was just a matter of time before America entered the War with the Allies (this of course is debatable, since it was Germany that declared war on the US). If Russia attacked he would be in srious trouble. Anyways, all that doesn't matter, to Hitler there was no question Russia must be defeated and White Russia used for Lebanstrom, controling the Center of Europe, therefore controlling the world or at least that is what Hitler believed.