The planned relocation of 8,000 U.S. Marines from Okinawa to Guam will suffer a setback if Tokyo does not abide by other agreements on the realignment of U.S. forces in Japan, U.S. Secretary of Defense Robert Gates said Wednesday.

Gates, in Tokyo to lay the groundwork for President Barack Obama's visit to Japan next month, advised the Democratic Party of Japan-led administration to stick to the 2006 agreement and relocate U.S. Marine Corps Air Station Futenma to another location within Okinawa.

"We are very sympathetic to the desire of the government in Japan to review the realignment road map," Gates said of the relocation of Futenma following a meeting with Defense Minister Toshimi Kitazawa. But he insisted that relocation of the air station as planned is the "linchpin" of the program.