Worried about a new direction in Japan's foreign policy, the Obama administration warned the Tokyo government Wednesday of serious consequences if it reneges on a military realignment plan formulated to deal with a rising China. The comments from Defense Secretary Robert M. Gates underscored increasing concern among U.S. officials as Japan moves to redefine its alliance with the United States and its place in Asia. In August, the opposition Democratic Party of Japan (DPJ) won an overwhelming victory in elections, ending more than 50 years of one-party rule. For a U.S. administration burdened with challenges in Pakistan, Afghanistan, Iraq, Iran, North Korea and China, troubles with its closest ally in Asia constitute a new complication. A senior State Department official said the United States had "grown comfortable" thinking about Japan as a constant in U.S. relations in Asia. It no longer is, he said, adding that "the hardest thing right now is not China, it's Japan." The official, who spoke on the condition of anonymity because of the sensitivity of the issue, said the new ruling party lacks experience in government and came to power wanting politicians to be in charge, not the bureaucrats who traditionally ran the country from behind the scenes. Added to that is a deep malaise in a society that has been politically and economically adrift for two decades. In the past week, officials from the DPJ have announced that Japan would withdraw from an eight-year-old mission in the Indian Ocean to refuel warships supporting U.S.-led coalition forces in Afghanistan. They have also pledged to reopen negotiations over a $26 billion military package that involves relocating a U.S. Marine Corps helicopter base in Japan and moving 8,000 U.S. Marines from Japan to Guam. After more than a decade of talks, the United States and Japan agreed on the deal in 2006. The atmospherics of the relationship have also morphed, with Japanese politicians now publicly contradicting U.S. officials. U.S. discomfort was on display Wednesday in Tokyo as Gates pressured the government, after meetings with Prime Minister Yukio Hatoyama, to keep its commitment to the military agreement. "It is time to move on," Gates said, warning that if Japan pulls apart the troop "realignment road map," it would be "immensely complicated and counterproductive." In a relationship in which protocol can be imbued with significance, Gates let his schedule do the talking, declining invitations to dine with Defense Ministry officials and to attend a welcome ceremony at the ministry. Hatoyama said Gates's presence in Japan "doesn't mean we have to decide everything." For decades, the alliance with the United States was a cornerstone of Japanese policy, but it was also a crutch. The ruling Liberal Democratic Party (LDP) outsourced many foreign policy decisions to Washington. The base realignment plan, for example, was worked out as a way to confront China's expanding military by building up Guam as a counterweight to Beijing's growing navy and by improving missile defense capabilities to offset China and North Korea's increasingly formidable rocket forces. The DPJ rode to power pledging to be more assertive in its relations with the United States and has seemed less committed to a robust military response to China's rise. On the campaign trail, Hatoyama vowed to reexamine what he called "secret" agreements between the LDP and the United States over the storage or transshipment of nuclear weapons in Japan -- a sensitive topic in the only country that has endured nuclear attacks. He also pushed the idea of an East Asian Community, a sort of Asian version of the European Union, with China at its core. Soon after the election, U.S. officials dismissed concerns that change was afoot, saying campaign rhetoric was to blame. Although most of those officials still say the alliance is strong, there is worry the DPJ is committed to transforming Japan's foreign policy -- but exactly how is unclear. DPJ politicians have accused U.S. officials of not taking them seriously. Said Tadashi Inuzuka, a DPJ member of the upper house of Japan's parliament, the Diet: "They should realize that we are the governing party now." Kent Calder, the director of the Edwin O. Reischauer Center for East Asian Studies at Johns Hopkins University and a longtime U.S. diplomat in Japan, said that if Hatoyama succeeds in delaying a decision on the military package until next year, U.S. officials fear it could unravel. Other Asian nations have privately reacted with alarm to Hatoyama's call for the creation of the East Asian Community because they worry that the United States would be shut out. "I think the U.S. has to be part of the Asia-Pacific and the overall architecture of cooper