China will likely use its growing power to try to force its way with Japan but it is doubtful that Beijing will enter a Cold War-style confrontation with the United States, a study said.
The report by the Washington-based Carnegie Endowment for International Peace aims to be the most comprehensive unclassified assessment of China's rise and its impact on the US-Japan alliance in the years ahead.
China, which has been boosting its defense spending by double digits each year, has an increasingly tense relationship with Japan, which has voiced alarm at the frequency of Chinese ship incursions around disputed islands.
The report said China likely saw force as a last resort in foreign affairs but that Beijing may see its interests in the islands -- known as the Senkaku in Japanese and Diaoyu in Chinese -- as a special case.
"The most likely potential challenge to the US-Japan alliance over the next 15 to 20 years does not involve full-scale military conflict between China and Japan or the United States -- for example, one originating from Chinese efforts to expel Washington from the region," it added.
"The likeliest challenge instead stems from Beijing's growing coercive power -- increasing Chinese military capabilities could enable Beijing to influence or attempt to resolve disputes with Tokyo in its favor short of military attack."
"Dramatic shifts" -- such as an Asian Cold War pitting China against the United States and its allies, or the dawn of a Chinese-dominated Asia -- are unlikely by 2030, according to the study.
The 395-page report was written by nine experts led by Michael Swaine, a veteran US specialist on Chinese security. It faulted previous studies for looking only at military factors or making worst-case assumptions on China.
The study identified two likeliest scenarios for China. In one, its economy would grow at between four and five percent annually -- a more modest pace than in recent years -- and the leadership would focus on domestic stability.
Under such a scenario, China would adopt a "restrained and largely defensive stance" toward Japan and the US-Japan alliance over the next 15 to 20 years, largely in keeping with recent policy.
But under another scenario also seen as likely, China would post higher growth and take an increasingly assertive posture. China would probably try more actively to pressure Japan, but would also seek economic cooperation and attempt to avoid "excessive alarm" in Tokyo and Washington.
Japanese Prime Minister Shinzo Abe, a conservative who returned to power in December, has moved to step up defense spending by the world's third largest economy and supports revisions to the post-World War II pacifist constitution.
But the study doubted major changes by Japan toward China due to factors that include the constitution, a likely slow-growing economy, an aging population and business interests involving the larger neighbor.
"Despite the recent ascendancy of those who advocate a full-blown competitive strategy, Japan is more likely to pursue a policy of cooperative engagement that encompasses either a hard or soft hedge," the report said.
Japan is expected to put a top priority on its alliance with the United States, even amid expectations that Washington will scale back its military, the report said.