Answer:
Sure they can, they are both members of the cat family and can easily interbreed but the chances of this happening in nature are slim given that White Tigers are Bengal Tigers which live in Northern Asia and the Siberian Tiger lives in Siberia and other parts of Russia.
If you are asking whether a Siberian tiger could mate with a white Bengal tiger, then yes it could, but not in the wild. Scientists believe that when a white Siberian tiger is born, it is more likely to be the result of human intervention; Previously mating a Siberian tiger and a Bengal tiger, which carries the white gene, leaving offspring as carriers. see related link..