A series of recent blunt statements from U.S. officials have left no doubt that Washington blames China's maritime expansionism for rising tensions in Asia. Now, America's main ally in the region needs to hear a similarly forthright message.

Japan had been clamoring for the U.S. to speak out more forcefully after China imposed an “air-defense identification zone” over a set of islands claimed by both countries. Officials in Tokyo have warned that any hint of daylight between Americans and Japanese only encourages further bullying from the mainland. For that same reason, U.S. officials have tempered their criticism of statements and actions by Japanese leaders that irk China, not to mention other victims of Japanese aggression during World War II.

This circumspection is becoming counterproductive. Since China imposed its air-defense identification zone in November, Japanese Prime Minister Shinzo Abe has visited the deeply controversial Yasukuni shrine, which honors, along with millions of fallen soldiers from various conflicts, 14 Class A war criminals from World War II. What's more, several of Abe's nominees to the board of the state broadcaster NHK have made appallingly retrograde comments that Abe has declined to disavow. One claimed the horrific 1937 Nanjing Massacre never took place, while another pooh-poohed complaints that the Japanese military had exploited thousands of women from Korea and elsewhere as sex slaves during the war. Other Abe allies are busily trying to rewrite textbooks to downplay Japan's wartime brutality.

Japanese officials seem unconcerned with the impression all this creates abroad, arguing that relations with China and even with fellow U.S. ally South Korea can hardly get worse, and in any case are unlikely to improve so long as nationalists remain in power in those countries. A more conciliatory Japanese attitude, they are convinced, would only prompt endless humiliating demands from Beijing and Seoul.

Worse, Japan seems to be taking U.S. backing for granted. Abe went to Yasukuni even after Vice President Joe Biden quietly urged him not to. Details of their conversation were then strategically leaked, presumably to showcase Abe's defiant stance. In private, Japanese officials snipe about the Barack Obama administration’s alleged unreliability. Anything other than unstinting support for Japan is taken as a lack of backbone.

The U.S. should push back, and less gently than usual. President Obama's trip to Asia in April is an opportunity for the White House not only to reaffirm its disapproval of Chinese adventurism but also to make clear that Abe’s provocations are threatening stability in the region, and damaging the U.S.-Japan alliance.

This won’t change many minds inside Abe’s inner circle, of course. But most Japanese are acutely sensitive to any hint of U.S. displeasure. (Nearly 70 percent of respondents to one poll called on Abe to heed the negative reaction to his Yasukuni visit, which included a mild expression of “disappointment” from U.S. Ambassador Caroline Kennedy.) Voters threw out Abe once before when he let nationalist obsessions distract him from minding the economy. Sustained domestic pressure is needed to rein him in again.

Abe is not necessarily wrong to want to make Japan a more muscular nation -- to rejuvenate its economy, open up its society and normalize its self-defense forces. A more robust Japanese military could play a bigger role in promoting global and regional stability -- whether through anti-piracy patrols or peacekeeping missions -- and come to the defense of its allies. Inflaming Chinese and Korean sensitivities helps achieve none of those goals.

All it does is raise the likelihood of conflict in the region. That Abe's recent actions and comments may be less dangerous than China’s adventurism is beside the point. He’s eroding the international goodwill that Japan has built up over decades as a responsible democracy -- all for no good reason. If he can’t see that for himself, perhaps the U.S. -- and his own citizens -- can help him.

To contact the editor responsible for this article: David Shipley at davidshipley@bloomberg.net.