A hard-won agreement to move thousands of U.S. Marines to a new base in Okinawa is once again in doubt as top U.S. and Japanese officials sit down for talks in Washington Tuesday.

The 2006 agreement called for a new base to be completed in a less congested part of Okinawa by 2014 and for 8,000 Marines to be moved with their families to the U.S. island of Guam.

But officials on both sides now say that timetable is unrealistic and a postponement will be announced after Tuesday's meeting. Secretary of State Hillary Clinton and Defense Secretary Robert Gates will host Japanese counterparts Takeaki Matsumoto and Toshimi Kitazawa at the talks.

The delay is likely to cause fresh frustration in Okinawa, where many residents would like to see the Marines leave altogether. British journalist David McNeill, a regular visitor to Okinawa, tells VOA that 75 percent of all U.S. military facilities in Japan are concentrated in the small, heavily populated island.

Under the 2006 agreement, Japan is to pay about $6 billion of the cost of the move, with the United States to pay the remainder. But work was delayed by the election of a new Japanese government that initially objected to the project, leading to the resignation of former Prime Minister Yukio Hatoyama.

The plan was further delayed by Japan's March 11 earthquake and tsunami, which will require a massive rebuilding effort.

On the American side, three influential senators are leading resistance to the plan in Congress, where many consider the scheme too costly at a time of high budget deficits.

At their talks Tuesday, the officials are also expected to discuss North Korea's nuclear program and other issues.