TOKYO -- When President Bill Clinton signed a 1994 agreement promising to "respect" the territorial integrity of Ukraine if it gave up its nuclear weapons, there was little thought then of how that obscure diplomatic pact -- called the Budapest Memorandum -- might affect the long-running defense partnership between the United States and Japan.
But now, as U.S. officials have distanced themselves from the Budapest Memorandum in light of Russia's takeover of Crimea, calling promises made in Budapest "nonbinding," the United States is being forced at the same time to make reassurances in Asia. Japanese officials, a senior U.S. military official said, "keep asking, 'Are you going to do the same thing to us when something happens?' "
For Defense Secretary Chuck Hagel, who arrived Saturday in Tokyo for two days of talks with Japan's leaders, including Prime Minister Shinzo Abe, America's long-standing promise to protect Japan against hostile nations -- read China and North Korea -- has suddenly come under the microscope. The U.S. response to the Russian takeover of Crimea, which President Barack Obama has condemned while at the same time ruling out U.S. military action, has caused deep concern among already skittish Japanese officials.
"The Crimea is a game-changer," said Kunihiko Miyake, a former adviser to Mr. Abe who is now research director at the Canon Institute for Global Studies in Tokyo. "This is not fire on a distant shore for us. What is happening is another attempt by a rising power to change the status quo." He pointed as an example to China's challenge to Japanese control of the Senkaku Islands, the uninhabited rocks in the East China Sea that Beijing claims under the name Diaoyu Islands.
One Japanese official said, speaking on the condition of anonymity, said, "We are just looking for a commitment from the American side."
Obama administration officials say they stand by the U.S. commitment to protect Japan, while refraining from explicitly stating that the United States would intervene militarily in the Senkaku Islands dispute.
"There is no indication or weakness on the part of the United States as to our complete and absolute commitment to the security of Japan," Mr. Hagel said, speaking to reporters aboard his flight to Japan.
"We will make that again clear over the next two weeks," he added, referring to his own meetings with the Japanese as well as Mr. Obama's planned trip to the region later this month.
Upon landing at Yokota Air Base just outside Tokyo to speak to a group of American and Japanese troops, Mr. Hagel said he was in Japan to reaffirm America's "continued commitment to our partnership, our friendship and our treaty obligations."
"We are serious about that," he said.
A Defense Department official traveling with Mr. Hagel pointed on Saturday to the mutual security treaty between the United States and Japan as proof that the United States would protect Japan if necessary. "There is absolutely no wavering," he said.
But in meetings over the last few weeks, Obama administration officials said, Japanese officials have been seeking reassurances that the security treaty will apply to the Senkakus.
Last year, China set off a trans-Pacific uproar when it declared that an "air defense identification zone" gave it the right to identify and possibly take military action against aircraft near the islands. Japan refused to recognize China's claim, and the United States has been defying China ever since by sending military planes into the zone unannounced, even as the Obama administration advised U.S. commercial airlines to comply with China's demand and notify Beijing in advance of flights.
The chief of staff of the Japanese military's joint staff, Gen. Shigeru Iwasaki, met Thursday with Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, in Washington to discuss security concerns. The two men "addressed geopolitical trends in the Asia-Pacific region and the need to strengthen the alliance's deterrence and response capability," the Pentagon said after the meeting.
U.S. officials say there is a wealth of difference between Ukraine and Japan, and between Crimea and the Senkakus. What is more, they say, there is a big difference between the Budapest Memorandum and the mutual security treaty with Japan that was signed in 1952 and has redefined American-Japanese relations in the 60 years since.
The treaty, which also provides for the continued presence of U.S. military bases in Japan, establishes that any attack against Japan would require the United States to respond. The Budapest Memorandum, by contrast, simply refers to security assurances for Ukraine that are not defined, and have been widely interpreted as less than a military guarantee of intervention.