BERLIN (Reuters) - European fans will cheer on U.S. presidential candidate Barack Obama as he visits Berlin, Paris and London this week, but governments wary of his inexperience and evolving policies fear the euphoria is overdone.

Largely an unknown quantity in Europe, the Democratic contender is due to land here on Thursday, kicking off the second part of a foreign tour that began in the Middle East with a speech on trans-Atlantic relations in the German capital.