WASHINGTON — The Democratic Party of Japan's setback in the Upper House election may complicate attempts by Tokyo and Washington to "reset" their political relationship, strained over the relocation of the Futenma military base in Okinawa, according to U.S. experts.

"The Japanese are going to be embroiled in their own domestic politics for quite a while to come, and there's not going to be a lot of bandwidth" for dealing with the United States, said Dan Sneider, a Japan expert at Stanford University's Freeman Spigoli Institute.

The replacement of Yukio Hatoyama by Naoto Kan as prime minister appeared to provide an opportunity for the DPJ-led government to reset relations with the United States, which got off to a rough start following the DPJ's landslide victory over the long-reigning Liberal Democratic Party last August.