There's further uncertainty over the US military's planned build-up on Guam after Japan's Prime Minister again delayed a decision over a major troop relocation plan for at least another six months.
Prime Minister Yukio Hatoyama on Friday said the decision on where to relocate the Marine Air Station at Futenma in Okinawa would not be reached at the end of May as he previously promised.
The relocation of the base has been a point of contention between the US and Japan since Mr Hatoyama took office last year.
Having committed to appeasing Okinawans who want the air base removed from Okinawa entirely, Mr Hatoyama has been urging US officials to rework the terms of a 2006 bilateral agreement.
Part of that agreement is the transferral of 8,000 Marines from Okinawa to Guam by 2014.
The US Defense Secretary Robert Gates has said he doesn't see that happening if the US and Japan don't reach agreement on the relocation of Futenma.