The United States hopes Japan's Upper House election will bring political stability to its key regional ally that will in turn yield progress on long-pending bilateral issues, an expert on Tokyo-Washington relations said.

"What the American officials want is . . . political stability" in Japan, said Mike Mochizuki, associate professor of political science and international relations at George Washington University.

Bilateral negotiations over key issues, such as the relocation of the U.S. Futenma air station in Okinawa Prefecture and Japan's participation in the Trans-Pacific Partnership trade talks, have become bogged down by the revolving door of prime ministers in Tokyo.