The next prime minister faces a possible showdown with Washington over a plan to relocate a U.S. air base in Okinawa and in the process move thousands of U.S. Marines from the prefecture to Guam, as he tries to remake his country's relationship with the U.S. while maintaining their strong alliance.

Yukio Hatoyama, riding a landslide victory by his Democratic Party of Japan in Sunday's Lower House election, is expected to be formally voted in as prime minister Sept. 16, ending more than a half-century of almost uninterrupted rule by the staunchly pro-Washington Liberal Democratic Party.

Although Hatoyama is facing a mountain of economic problems, including Japan's worst unemployment rate since World War II, attention is also keenly focused on his ability to fulfill promises that he will remake Tokyo's relationship with Washington. Hatoyama has said he wants Japan's relationship with the U.S. — a key trade partner and the Asian power's strongest ally — to be more equal.