iStockphoto/Mark Gabrenya

Just days before his party took power in September, Democratic Party of Japan (DPJ) lawmaker Tsuyoshi Yamaguchi stated that missile defense was "almost totally useless." That week, as DPJ leader Yukio Hatoyama became Japan's prime minister on Sept. 16, Japan Air Self-Defense Forces shot down a mock ballistic missile over the skies of New Mexico.

Which security policy approach will survive under Japan's new government? The answer has implications not only for Japan, but also for the United States' position in Asia. Mr. Yamaguchi's statement cannot be dismissed out of hand, since he served as the party's deputy defense spokesman before the historic elections that turned over power to an opposition party for only the second time in half a century. In an interview with Japanese press, Mr. Yamaguchi asserted that the DPJ will likely cut defense spending in order to push through with domestic entitlement plans, "such as child care allowance, education, health care and pensions." Yet, as Japan's second successful test shows, Tokyo's partnership with the United States on missile defense is continuing to develop and show promise just as North Korea continues its missile program and China further beefs up its rocket forces.

Missile defense development is not cheap, especially in a period of flat defense spending. Japan's Ministry of Defense has requested just under $2 billion for missile defense programs, out of a total defense budget of $53 billion (at current exchange rates). Yet missile defense is also just one part of the larger movement in Japan's military development over the past decade. The ministry is also in the midst of selecting its next generation air defense fighter and continuing a modernization of naval assets, including more Aegis-equipped destroyers and upgrading its aging P3-C surveillance planes. These are expensive, long-term investments that will shape the Japanese military, and influence the U.S.-Japan alliance, for years to come. And yet, the new government has given almost no indication of what its own security policies will be or how it will structure the defense budget in the coming years.

Like all leaderships, Japan's new national security team must prioritize its spending plans. Over the last decade, since North Korea launched a Taepodong ballistic missile over Japanese airspace in 1998, Tokyo has aggressively funded programs aimed at emerging threats. In doing so, it has worked more closely with Washington than any other American ally. It has deployed land-based PAC-3 batteries, sharing information with U.S.-operated X-Band radars in Japan, and has installed sea-based SM-3 systems on four Aegis destroyers.

In that time frame, Japan's neighbors have developed other offensive weapons systems, thus giving Tokyo further incentive to continue defensively based programs. Pyongyang has launched short, medium, and long-range ballistic missiles in 2006 and 2009, as well as set off two small-scale nuclear explosions. Meanwhile, China has introduced the Jin class of nuclear-powered ballistic missile submarine, extended the operations of its diesel submarines, and further refined its mobile medium and intermediate-range DF-21 ballistic missiles. Russia has returned to the skies, as well, doing frequent fly-bys of Japanese territory with strategic bombers.

All of which brings us back to Mr. Yamaguchi's statement on the uselessness of missile defense. His comments garnered attention because they are among the very few pieces of evidence foreign observers have for DPJ thinking on security policies. The recent elections in Japan were about domestic issues, and Mr. Hatoyama's election manifesto was heavy on social and economic reform, with little discussion of foreign and security policy plans. Yet, since taking power in September, Mr. Hatoyama has restructured the way policy is made in Japan, so that backbenchers like Mr. Yamaguchi are finding themselves frozen out of the decision making process, according to Japanese bureaucrats familiar with the situation. Under the long-ruling Liberal Democratic Party, initial policy was set inside the party and then sent to the Diet and Cabinet Office. Mr. Hatoyama has instead centralized policymaking inside the Cabinet Office, which actually continues the trend of strengthening central power that started with LDP prime ministers Junichiro Koizumi and Shinzo Abe.

Yet the very tightness of control means that the new government's security policy goals are harder to discern in the absence of any clear statements by principal players. The DPJ's election manifesto included a promise to "re-evaluate" missile defense, and said nothing about overall force modernization. Thus the attention given to Mr. Yamaguchi's statement, despite that fact that he likely has little influence currently. Analysts wonder, though, though whether his views are shared by Mr. Hatoyama or others in the leadership circle. On a positive note, alliance watchers were heartened when DPJ politician Akihisa Nagashima was named vice minister for defense. Nagashima is well known in Washington circles as a strong supporter of the alliance, but he still must take his cues from Mr. Hatoyama and Foreign Minister Katsuya Okada, with whom he is close.

The Cabinet's foreign policy goals are clearer. Under the long-time leadership of Ichiro Ozawa, the DPJ has called for closer relations with China. Mr. Ozawa, who now holds the number two-position in the party under Mr. Hatoyama, led a 500-person delegation to Beijing in December 2007 at the height of his power. Prime Minister Hatoyama ran on improving Japan's relations with Asian nations, something that would benefit the U.S.-Japan alliance, as well, but not if the result was a Japanese move to limit our cooperation on key security issues. This past weekend, Prime Minister Hatoyama joined Chinese President Hu Jintao and South Korean President Lee Myung-bak in Beijing, where all three pledged to more closely coordinate trilateral cooperation on economic growth and climate change. Mr. Hatoyama has called for a new East Asian community, moreover, that would possibly deal even with security issues, though what role the United States would play in Mr. Hatoyama's scheme remains unclear.

In contrast to foreign policy, DPJ statements on the alliance are murky, often resulting from the need to play to domestic constituencies. It has indicated it wants to re-negotiate parts of the Status of Forces Agreement governing the U.S. military presence in Japan, and most controversially, reconsider key agreements relating to the relocation of U.S. forces on Okinawa, particularly the location of the Futenma air station replacement. Mr. Hatoyama has repeatedly said that the cornerstone of Japanese security will remain the alliance with Washington, but specifics will now be judged more heavily than rhetoric. U.S. diplomats I talked with recently in Japan are confident that our agreements with Tokyo will go forward without serious disruption, but there is still the question of the DPJ's long-term security vision.

If Japan under the DPJ ends its Indian Ocean refueling mission (which seems almost certain), slows military modernization, and curbs missile defense, while further engaging China and looking to U.N. sanctions to solve the North Korean nuclear crisis, then Washington may well re-evaluate how aligned its security goals are with Tokyo's. Few analysts, including this one, doubt that in a real Asian military crisis, Washington and Tokyo would work together and both partners would uphold their alliance commitments. But events are much more likely to drift than to come to a sudden head. The reality is that a gradual shift in strategic vision, shared agendas, and underlying political will on the part of Tokyo and Washington will more likely determine how credible each nation's security policies remain and how closely they view each other as key security partners.

The Asian strategic environment is not static, and a diminution of Japanese capability in light of China's growing strength, or a reverse course on promising missile defense programs in the shadow of Pyongyang's provocations, will present Washington with uncomfortable choices. It also may cede, unnecessarily, Japan's role as a liberal leader in Asia. Diplomatic engagement of the kind proposed by Japan's new leadership is important and should be encouraged. But it is only part of the strategic equation, not the whole.

Michael Auslin is a resident scholar at AEI.