WASHINGTON — The United States appears increasingly concerned about the new course of Japan's foreign policy, raising the specter of a showdown between Prime Minister Yukio Hatoyama and President Barack Obama at their summit in Tokyo next month.

At the center of the widening gap is the fate of the 2006 bilateral deal to reconfigure U.S. forces stationed in Japan, especially the relocation of the Futenma air base in Okinawa.

Among the Democratic Party of Japan's campaign pledges in the general election was transferring the airfield outside Okinawa or even outside Japan.