Japan's Prime Minister Yukio Hatoyama returned home from Washington this week a considerably diminished leader.

By rights, Hatoyama ought to have shone at a meeting of world leaders convoked to find ways to lessen the dangers of nuclear terrorism or nuclear conflict. After all, Japan is the world's only victim of an atomic bomb attack and has championed every initiative to reduce the role of nuclear weapons.

It is also a country that holds one of the world's largest stockpiles of plutonium -- enough it is said, to build hundreds if not thousands of atomic bombs if the right kind of stuff fell into the hands of nuclear terrorists.

But all Japan had to offer at the conference was plan to establish a "center to enhance human resources development preventing nuclear terrorism" at its Tokai nuclear power research facility north of Tokyo with an initial budget of about $2 million. That hardly stood out among the several major announcements that emanated from the nuclear summit meeting, such as Ukraine's offer to surrender stockpiles of highly enriched uranium or Russia's announcement that it planned to close a reactor used to make weapons-grade plutonium.

Hatoyama was not among the world leaders who were accorded an opportunity for a formal bilateral meeting with President Barack Obama. He had to settle for 10 minutes seated next to the American president at an opening dinner. It is reported that he used this brief encounter to try to reassure Obama that his government was finding a solution to the intractable problem of relocating the US Marine Corps Air Station on Okinawa, a long-festering issue between the two countries and Japan's own citizens. But in the context of a summit on nuclear terrorism, it must have seemed unbelievably parochial to Obama.

May is shaping up to be the critical month for Japanese politics. Of course, the end of May is the time when the prime minister has promised to offer an alternative solution to moving the Futenma Marine base to another more remote location on Okinawa.

Increasingly, it looks like the premier is betting his job on the doubtful proposition that he can square the circle and come up with a solution that both satisfies Washington and Tokyo and the local authorities for wherever he plans to place the base.

Much speculation centers on a proposal to split the Futenma functions between a relatively small helicopter pad to be built at the Camp Schwab Marine base with a larger air field constructed on an island called Tokunoshima, at the near end of the chain of islands stretching west from the mainland across the East China Sea.

In this scenario Hatoyama could proclaim that he has moved most of the base out of Okinawa, as promised, since Tokunoshima is technically in Kagoshima prefecture at the western end of Kyushu. But the proposal is fiercely opposed by the locals as well as the prefectural governor.

Nor is there any indication that Washington would agree to the new arrangement. It has stated previously that it doesn't want the functions of Futenma broken up in this manner. It is also not likely to okay a deal that does not have some local approval.

It is hard not to conclude that the prime minister has bungled this issue royally. First, he delayed a decision until the people of Nag, the city surrounding the proposed new airfield, held their mayoral election in January. Predictably, the voters ousted the pro-base mayor and installed another mayor opposed to the relocation.

In the seven months he has been in office Hatoyama has done little to try to persuade local officials to accept the facility in the interests of the nation. Though a globetrotter, he has yet to visit Okinawa and has only met with the prefectural governor once.

It is fair to say that nobody in the Democratic Party of Japan (DPJ) imagined that the base issue would snowball into Japan's biggest foreign policy issue. The party came into office in the wake of its historic election triumph last summer wanting to fix the economy, redirect spending priorities and enshrine cabinet, rather than ministerial government.

The party's election manifesto hardly made any mention of Okinawa; nor was it much of an election issue. Yet, for some reason, Hatoyama fixed on the notion that moving the base out of Okinawa was an unbreakable promise. Now a failure to satisfactorily resolve the impasse could lead to his early resignation.

In a recent survey by the Yomiuri newspaper, some 49 per cent said he should step down if the row isn't settled by the end of May. It's not that most mainland Japanese are so concerned about the base issue, but they think it has exposed the premier's deficiencies as a leader. Meanwhile, the cabinet's overall approval ratings have sunk to the low 30s.

May is also a critical month in that both the DPJ and the now opposition Liberal Democratic Party (LDP) will be gearing up for the election in July for one half of the House of Councilors, the upper house of Japan's bicameral legislature.

The party is still hoping that it can win an absolute majority by itself, and not have to depend on the support of two small coalition partners to pass bills. Now people are beginning to wonder whether the party can keep its majority even with the support of the two smaller parties.

If the DPJ should lose seats in the upper house election, it would almost certainly force Hatoyama to resign, turning him into yet another "one-year wonder". (The three previous LDP premiers resigned after less than one year in office.)

Should he resign, the premiership could fall to his deputy, Naoto Kan. Speaking to foreign journalists recently Kan tried to stick to economic issues and eschew political topics as he is also the finance minister.

He did allow that it was his personal belief that Japanese prime ministers ought to serve at least four years in office. It has been a while since any premier came close to that kind of longevity in office, and anybody betting on Hatoyama to break the pattern might be on a fool's errand.