In form, the meeting between Mr Clinton and the Japanese Prime Minister, Ryutaro Hashimoto, has been conventional enough. But the contrasts with previous summits, dominated by fractious arguments about trade, are striking.
The joint statement exchanged by the two leaders in front of the Akasaka Palace yesterday was itself an indication of the change of emphasis. The meat of the agreement was about security, a forceful confirmation of the status quo in the face of gathering uncertainty inside and outside Japan.
The Joint Declaration on Security contains no surprises. The US will maintain 100,000 forward-deployed troops in Asia, and around 47,000 of these, the same number as before, will be based in Japan. The two sides will continue to cooperate on intelligence-gathering and strategy in times of crisis, and jointly develop the F2 support fighter. Tokyo will continue to pay for the maintenance of its military guests; Washington will continue to support Japan's bid for a permanent seat on the UN Security Council.
But behind all this mutual reaffirmation there is more than a little nervousness, and it comes at a crucial moment, both for Asian security as a whole and for America's particular interests in Japan.
Touted in the Joint Declaration as a celebration of "one of the most successful bilateral relationships in history", the summit is in many ways the culmination of a giant damage limitation exercise which began last September after the rape of a 12-year-old Japanese schoolgirl by three US servicemen on the island of Okinawa.
The crime galvanised long-standing resentment on the island, where three- quarters of all US bases and 29,000 US troops are concentrated. In October, 85,000 Okinawans rallied in protest at the US presence. The Prefecture Governor, Masahide Ota, refused to sign documents necessary for the compulsory leasing of land used by the bases. The dispute remains embarrassingly unresolved.
The Okinawa issue was in part pre-empted by the unveiling on Monday of an American plan to return one-fifth of the Okinawan land currently occupied by the bases. The cost, to be met by the Japanese, is estimated at 1 trillion yen.
But the visit is also a reflection of wider anxieties about Asia. Mr Clinton visited the aircraft carrier Independence which, less than a month ago, was nervously watching over Chinese missile tests in the Straits of Taiwan. Earlier, he and Mr Hashimoto discussed the situation on the Korean border, where North Korean troops violated the armistice earlier in the month. If war did break out on the peninsula, the American military effort would be supplied and coordinated from Okinawa.
But a fog of ambiguity surrounds Japan's actual role in the event of an emergency. Under the post-war constitution Japan is forbidden from "the use of force as a means of settling international disputes". Its military is strictly designated as the Self Defence Force. Any suggestion that it might operate outside the confines of Japanese territory is profoundly controversial.
US officials refuse to be drawn into discussion of another country's constitutional dilemmas; the Japanese say vaguely that their response to an emergency will depend on what that emergency may be. As Mr Clinton and Mr Hashimoto shook hands yesterday, there was a strong suspicion they were crossing their fingers behind their backs, and hoping their grand words would never be tested.