TOKYO, AUG. 13 -- Japanese Prime Minister Toshiki Kaifu made a last-minute decision today to call off his long-planned trip to the Arabian peninsula because of the military crisis that has developed in the region resulting from the Iraqi invasion of Kuwait.

Kaifu was scheduled to leave Wednesday, but canceled the trip after discussions with his foreign minister, Taro Nakayama. Foreign Ministry officials had said they were concerned that a Kaifu visit now might leave the appearance that Japan was engaged in a desperate drive to obtain new oil supplies in the wake of the worldwide embargo on Iraqi oil.

Months ago, when the Arabian peninsula was at peace, Kaifu scheduled a summer trip to several Arab nations, with departure set for Aug. 15 -- this Wednesday. All last week, Kaifu insisted that he still planned to go, crisis or no crisis. But over the weekend, the trip became the topic of intense debate within Kaifu's cabinet.

The change in Kaifu's travel plans reflects a larger sense of uncertainty that Japan seems to feel as it begins to take a bigger role in international affairs.

Since its shattering defeat in World War II, Japan has been a reluctant player on the world stage, content to permit its Western allies to manipulate diplomatic and military affairs in other countries.

But now, as an economic superpower with trade routes to every corner of the world, Japan has become a major factor in international geopolitics. Just how that translates into day-to-day policy decisions is a question the Japanese are now struggling to answer.

When a top official of the Foreign Ministry here (who declined to be quoted by name) was asked this weekend what role Japan will play in resolving the Persian Gulf crisis, he sat in deep thought for a long time and then came up with an answer draped in ambiguity: "It will be an important role, but perhaps not a leading role."

To the extent that Japan has an international role, it is one based on money, not muscle. Under the post-war constitution written for this country by the U.S. occupation force, Japan cannot send its military forces overseas.

But this wealthy nation has taken an increasingly large role in world finances, both in the global operations of its business community and in government-to-government foreign aid. By some measures, Japan is now the largest granter of foreign aid in the world.

Japan's trade relations with the Persian Gulf are particularly important. The island nation gets 70 percent of its oil from the Mideast. Following Kaifu's decision last week to ban oil imports from Iraq and Kuwait, Japan is even more dependent on other Persian Gulf nations to meet its energy needs.

That means that Japan will be a major beneficiary of the allied military force now in the Arabian Peninsula to protect Saudi Arabia against Iraqi military force. Since Japan will make no military contribution to that allied effort, Foreign Ministry officials say they may consider looking for ways to help Japan's allies pay for the expedition.

"There is more awareness than there used to be {in the Japanese government} of the need to be a partner of the U.S. and the Western allies in international matters such as this one," the Foreign Ministry official said this weekend. "Since we cannot be a partner militarily, thought must be given to financial support and help on policy decisions."

It was largely an effort to expand awareness of Japan that prompted Kaifu to plan the Mideast trip. The prime minister's itinerary had called for a 12-day tour with stops in Turkey, Saudi Arabia, Oman, Jordan and Egypt, for what would have been the first Mideast visit by a Japanese prime minister in 12 years.

Kaifu has benefited noticeably in domestic political terms from other overseas trips, and he appears to love the experience. That may help explain why he kept saying he would make the scheduled trip even after the peninsula became a military hot spot two weeks ago. Kaifu said Thursday that the sole reason for his trip was to "see if Japan can contribute to the cause of peace in that region."

Some here feared that the trip's cancellation could threaten to turn Japan into nothing more than a spectator watching the allied peace effort from afar. The Japanese are worried about that prospect, for fear that it will make the country look once more as if it accepts help from its allies in tough situtations like this one without making any contribution in return.

On the other hand, some Japanese diplomats feared that a trip now would have made the country look greedy, with Kaifu touring Arab capitals hat-in-hand as if trying to squeeze more oil out of the gulf nations.