Tomorrow, Japan’s Shinzo Abe arrives in Washington, his first official visit to America as Japan’s leader. It is customary for Japanese prime ministers to come here on their first foreign tour or soon after assuming office, but Mr. Abe broke tradition.

He succeeded the charismatic Junichiro Koizumi last September and has already traveled widely. Mr. Abe’s first foreign visit was to Beijing, his second to Seoul. Since then, he has been to other parts of Asia and Western Europe. It almost seems as if he squeezed America into a tightly scheduled foreign tour as an afterthought. He will be here for less than two days on the opening stop of a trip that will take him to Saudi Arabia, the United Arab Emirates, Kuwait, Qatar, and Egypt.

During Mr. Abe’s stopover in Washington both he and President Bush will say that the relationship between the two countries is as strong as ever. It should be. America, after all, is Japan’s most important friend and the only nation that has pledged to defend the Japanese homeland with military force. Japan, as analysts say, is America’s “Britain of Asia.”

More important, the two nations face a common challenge: a rising China that has yet to become a constructive member of the international community — or a “responsible stakeholder” to use the State Department’s hopeful language. Furthermore, Japan and China are historical adversaries and have not come to terms over wars they waged against one another.

Mutual animosity over World War II, for example, has generally grown more intense as decades have passed. The two nations now compete for influence and view their relations as a zero-sum contest. They have territorial disputes not subject to easy compromise. They fear each other. The two of them for tactical reasons may tone down their rhetoric on occasion — as they have been doing for the past several months — but they have shown no moderation in their basic policies toward each other.

So President Bush and Mr. Abe should be standing shoulder to shoulder in more than just a literal sense when they meet. Yet there will be a distance between the two leaders for one reason — Japan worries that America will abandon it.

There are three primary reasons for Tokyo’s concern. First, there is no more Soviet Union to unite America and Japan in common cause. Second, Tokyo fears Washington’s repeated attempts to make friends with Beijing before it becomes benign. The third reason relates to Japan’s other adversary, the Democratic People’s Republic of Korea.

North Korea, as that nation is commonly known, views Japan as a criminal state deserving incineration. Pyongyang’s longest-range missile that is currently deployed, the one-stage Rodong, can put a 1,500-pound payload approximately 800 miles downrange. That’s far enough to hit the most populated parts of Japan.

The North is developing a nuclear warhead and is learning how to mate it to missiles — if it hasn’t mastered these tasks already. Even if North Korea’s leader, Kim Jong Il, cannot launch a nuclear-tipped missile today, he can now deliver an atomic bomb to Tokyo by merchant ship or pickup truck.

Washington’s response has been to cooperate with Tokyo on missile defense, but it has shown little interest in a solution that Japan wants: getting the Rodong out of Pyongyang’s inventory of launch vehicles. The Clinton administration ignored the Rodong threat to Japan just as the Bush administration is doing so now. Many speculate that Washington has never cared about this missile because it cannot reach the American homeland.

Just as bad from Tokyo’s perspective is President Bush’s decision to reach an accommodation with North Korea over its nuclear program. In February at the six-nation talks sponsored by Beijing, the Bush administration reversed six years of policy and accepted an interim deal that provides North Korea with aid — a million tons of heavy fuel oil — without requiring it to give up a single bomb or ounce of plutonium.

In arriving at this agreement, which Pyongyang has already violated, Washington first ignored and then undercut Tokyo’s efforts to use the Beijing talks to force North Korea to return Japanese citizens who had been kidnapped by that militant state.

Unfortunately, Tokyo is now isolated as none of the other parties at the negotiations is helping Japan to get back its citizens. Tokyo was so upset that it refused to make any contribution to pay for the fuel oil. Not surprisingly, tomorrow and the day after, Mr. Abe will complain to President Bush that the State Department has been meeting with the North Koreans without first consulting Japan.

The Japanese have consistently taken the toughest positions on North Korea at the six-nation talks — and at deliberations at the United Nations. Tokyo has advocated strict sanctions after the North Koreans tested missiles last July and a nuclear device last October. For the first time in more than six decades, Japan is taking a leading role in world affairs.

Japan has learned over the last year that America will not support its principled initiatives to disarm North Korea: Washington, unfortunately, has been giving in to Beijing’s demands on behalf of the North. If Washington’s softer policies don’t persuade Pyongyang to give up its nukes and missiles — and so far American strategies are failing — then Japan may lose confidence in American leadership and go its own way.

Mr. Chang is the author of “Nuclear Showdown: North Korea Takes On the World.”