Concerned about North Korea's ballistic missile development, the United States and Japan agreed Sunday to conduct joint research on a missile defense system that could protect the island nation from attack.

"No one should doubt our commitment to defend our interests and to work together for peace and stability in Asia," Defense Secretary William Cohen said at a joint news conference with Secretary of State Madeleine Albright and their Japanese counterparts. "And this is the best way to protect both the United States and Japan."The United States has 100,000 troops in the region, about one-third of them guarding the always tense demilitarized zone between North and South Korea.

Sunday's agreement comes after North Korea launched a rocket over Japan on Aug. 31 in a failed attempt to send a satellite into orbit. It was the latest example of Pyongyang's aggressive program to develop long-range missiles that could one day hit American shores, U.S. officials said.

Japan has conducted preliminary studies, some with the United States, on ways to defend against missiles. The United States is developing several theater missile defense systems as well, although American scientists haven't been able to overcome technological hurdles to knock a fast-moving target out of the sky.

Now, the United States and Japan will work together on research and development, which could lead to a missile defense system in the future. No target date was set.

"Our two countries will spare no efforts" to improve defense and security in the region, said Japanese Foreign Affairs Minister Masahiko Komura.

The United States, after Japan's surrender in World War II, pledged to defend the island nation - partly to contain its historic aggression. The two sides reaffirmed that security alliance on Sunday, and the Japanese agreed to legislatively approve revisions to increase cooperation as outlined in guidelines approved here last year.

How other Asian nations will respond to Sunday's announcement was not immediately clear, but China in particular long has been wary of any move toward rearming Japan.

The annual U.S.-Japan meeting of top defense and foreign affairs officials took place the day before the U.N. General Assembly begins two weeks of sessions.

Komura and Defense Minister Fukushiro Nukaga are new, coming in with Prime Minister Keizo Obuchi, who will hold his first talks with President Clinton on Tuesday. Clinton speaks to the General Assembly on Monday.

Clinton and Obuchi will discuss regional security matters too, but also will focus on Japan's faltering economy, with the president urging bank and other reforms to help reverse the Asian financial crisis now affecting other nations, including Russia and America.

Obuchi, in an interview withWestern reporters, said Saturday that Japan already had taken every measure to pull itself out of recession short of a "wartime economy" of massive military spending increases. He added that he would not resort to such a move, however.

Albright, in response to a reporter's question, said the administration was pleased by recent Japa-nese legislation to close or fix debt-ridden banks but was looking for more actions and for real results.

"I think they have taken an important step," Albright said. "Implementation is important."

Sunday the focus was security and defense.

In a joint U.S.-Japan statement, the two governments called on North Korea not to develop, test, launch or deploy missiles. They also urged a halt to North Korean missile exports to other countries, something the poverty-stricken Communist country is doing to raise cash.

In a related matter, the United States and Japan renewed their commitment to a 1994 international agreement with North Korea to freeze its nuclear weapons program in exchange for fuel oil and help in building two light-water reactors to meet energy needs.

The accord has been in danger of falling apart because of North Korea's missile tests, overdue fuel shipments and concerns about an underground facility in the closed country that U.S. intelligence suspects may be part of an attempt to revive its nuclear weapons program.

Japan, which is to contribute $1 billion towards the $4.6 billion cost of the light-water reactors, has delayed providing the money because of the Aug. 31 missile test. And the House last week voted to block $35 million to finance fuel deliveries to North Korea.

Komura said Japan still supports the so-called KEDO agreement, but fears that handing over the $1 billion now will signal to North Korea that its aggressive military actions don't have consequences.

"We cannot go ahead with the smooth contribution of $1 billion as if a missile launch had not taken place at all," the foreign minister said. "That would only send the wrong message to the North Koreans . . . that they will, with impunity, do almost anything at any time."