The United States warned Tuesday that Japan reneging on a bilateral deal to relocate a U.S. airfield within Okinawa Prefecture could harm the alliance between the two countries. State Department spokesman Ian Kelly issued the warning at a news briefing as he talked about Prime Minister Yukio Hatoyama’s stance of considering moving the U.S. Marines Futenma Air Station out of the prefecture as an option.
   
‘‘That’s a decision for the government of Japan to make…Ultimately, it’s for the government of Japan to decide what kind of relationship that they’re going to have with us,’’ he said.
   
As part of a 2006 bilateral accord on the reconfiguration of U.S. forces in Japan that took years to reach, the Futenma airfield is to be relocated from downtown Ginowan to Nago by 2014.
   
‘‘Our position on the agreements that we have for basing hasn’t changed,’’ Kelly said. ‘‘We think that this is the best way forward in our security relationship with Japan.’‘
   
The spokesman disputed the idea some Japanese government officials and ruling party lawmakers have expressed that the process of reaching the bilateral deal was not transparent.
   
The agreement with Japan ‘‘is designed to meet common challenges, common security challenges, and it’s done in complete transparency and in partnership with the government of Japan,’’ he said.
   
The United States has made it clear that Japan should come to a decision on where the Futenma base should be relocated in time for President Barack Obama’s Nov 12-13 trip to Tokyo—and in line with the existing bilateral deal.
   
But Hatoyama has said repeatedly that Tokyo will take time to consider the matter, adding he does not believe Japan has to reach a decision by the time he meets Obama.
   
Hatoyama’s Democratic Party of Japan, which came to power in September after a sweeping election victory, has promoted the idea of moving the air base out of Okinawa or even out of Japan.
   
Differences among Japanese cabinet members are compounding the issue, with Foreign Minister Katsuya Okada resisting the existing deal and floating the idea of transferring the base to the nearby U.S. Kadena Air Base.
   
Obama is scheduled to travel to Japan for talks with Hatoyama. Obama’s first visit to Japan since assuming office in January is part of his swing through Asia, which will also take him to Singapore, China and South Korea.