The U.S. military will probably scale back plans to build key bases in Japan and Guam because of political obstacles and budget pressures, according to U.S. and Japanese officials, complicating the Obama administration’s efforts to strengthen its troop presence in Asia.

Under a deal announced Wednesday with Japanese officials, the U.S. government said it will accelerate plans to withdraw 8,000 Marines from the island of Okinawa. The decision came after several years of stalled talks to find a site for a new Marine base nearby.

Washington’s inability to resolve its basing arrangements on Okinawa, as well as the rising price tag of a related plan for a $23 billion military buildup on Guam, underscore the challenges facing the Obama administration as it seeks to make a strategic “pivot” toward the Pacific after a decade of fighting wars in Iraq and Afghanistan.

The Japanese government said it is still committed to a 2006 accord with the United States to find a new base location for other Marines who will remain on Okinawa. But officials in Tokyo acknowledged that they had made little progress in the face of fierce resistance from islanders opposed to the long-standing U.S. military presence there. Bleak public finances in the United States and in Japan have also undermined the effort.

U.S. military officials had planned to relocate the 8,000 Marines and their families to Guam in 2014 as part of a massive military expansion on the U.S. territory in the Pacific. Japanese officials and media reported, however, that only 4,700 of the Marines would end up in Guam, a sign that the Pentagon is reconsidering its plans there.

Congress has questioned the cost of the Guam expansion and has ordered the Obama administration to take another look. Lawmakers have also asked the Pentagon to conduct an independent assessment of its overall deployment plans and troop presence in the Pacific region.

The administration has moved on a series of fronts to bolster the U.S. military presence in Asia and the Pacific recently. Officials reached a deal with Australia to deploy a small number of Marines to Darwin and are holding talks with the Philippines about expanding military ties.

Those moves, along with an agreement to station Navy ships in Singapore, are part of a broader strategy aimed at countering China’s rising influence in the region. Although the Obama administration wants to retain the bulk of U.S. forces in South Korea and Japan, where they have maintained a heavy presence since World War II and the Korean War, officials said they are looking to expand their presence in Southeast Asia.

“We are diversifying our strategic and military approach,” Kurt M. Campbell, the assistant secretary of state for Asian affairs, told a House subcommittee Tuesday. “We will keep a strong commitment in northeast Asia, but we will focus more of our attention in Southeast Asia.”

Reviewing the options

George Little, a Pentagon spokesman, said the military is reviewing its options on where to transfer the 8,000 Marines from Japan. “It’s premature to discuss troop numbers or specific locations,” he said Wednesday.

Under the 2006 accord signed by Tokyo and Washington, the Marines were to move to Guam only after Japan resolved one of its thorniest domestic issues: securing new land for an existing U.S. air base that most Okinawans don’t want on their island — in its current location or anywhere else.

The U.S. and Japanese governments long ago determined that the noisy Marine Corps Air Station Futenma, situated in the middle of a city, should be reconstructed on a northern and less populated slice of land in Okinawa. But they have been unable to begin work on the project, stymied by local opposition. Okinawans say they carry an inordinate burden by hosting, on various bases, more than half of the 50,000 U.S. troops stationed in Japan.

On Wednesday, U.S. and Japanese officials said they had lifted the requirement that Tokyo find a replacement for the Futenma base before the 8,000 Marines leave Okinawa. Although both sides said they will keep searching for a new location, the decision leaves Washington with much less leverage.

“We separated those two things in the package,” Japanese Foreign Minister Koichiro Gemba said. “The transfer of the Marines to Guam will not be related to progress in the relocation of Futenma station.”

By detaching the Guam move from the Futenma base controversy, the United States eased concerns that the 2006 accord was about to collapse. Gemba said he did not yet know a target date for the Marine transfer to Guam.

Sen. James Webb (D-Va.), a former Navy secretary and Vietnam veteran who is an influential lawmaker on Asian affairs, said the changes to the 2006 pact with Japan were necessary to “preserve the vital strength of our alliance and the stability of the region.”

Webb and other key senators have questioned the Pentagon’s planned military buildup in Guam, which could cost as much as $23 billion, according to some government estimates. The Pentagon is confronting a new era of austerity after a decade of flush budgets and is trying to slash about $490 billion in projected spending over the next 10 years.

Local opposition

The Futenma base sits in the middle of the city of Ginowan, surrounded by schools and houses. In 2004, a Marine helicopter crashed into a nearby college campus; no one died, but the incident inflamed an opposition that had existed for almost a decade, since the 1995 rape of an Okinawa 12-year-old by three U.S. servicemen.

In the agreement announced Wednesday, the United States and Japan reaffirmed their hope to relocate the base to a less-populated coastal area known as Henoko Bay. But so far, a series of Japanese prime ministers — each of whom survived only a short time in office — have been unable to gather support for that plan among Okinawa’s people and politicians.

“Okinawa’s opposition is still quite strong and still unified,” said Manabu Sato, a professor of political science at Okinawa International University. “Probably the obstacles are even greater than what the Japanese government in Tokyo expected. They have been trying to persuade the governor here to change his position by dropping a large amount of money and offering aid. But still the government maintains stiff opposition.”

Whitlock reported from Washington.