North Korea has softened its bargaining position on reunification and would agree to gradual economic and cultural ties with South Korea before political ties are established, according to a source close to the communist government in Pyongyang.

Such concessions by the North, which has launched an intense campaign to get unification talks under way, would represent a shift in Pyogyang's position, bringing it closer to the views of Seoul.

The change was explained yesterday by Pak Jae Ro, vice chairman of a large North Korean citizens' association in Tokyo. In an interview, he outlined a three-stage approach to unification that gives first priority to a series of gradually adopted exchange programs, cooperative agreements, military deescalation and diplomatic cooperation.

A year ago, the North was insisting on a political "confederation" of the two countires as the first step to emerge from unification talks. In contrast, the South was proposing a series of smaller steps, beginning with economic cooperation.

But in the interview yesterday, Pak in effect adopted the South's idea and said the first stage should consist of cooperative arrangements in economic, cultural, diplomatic and military fields.

The next step, he said, would be the "confederation," but he indicated that would start only after the cooperative agreements began to work and a feeling of "mistrust" between the two countries dissipated. Ultimately, he said, a "consensus" would appear on a single, unified state.

Pak is vice chairman of the central standing committee of the General Association of Korean Residents in Japan, which claims to represent about 600,000 Korean nationals who favor the communist government in Pyongyang.

Because of his frequent contacts with the Pyongyang government, he is regarded as a reliable guide to its political positions. Over a period of years, his comments have proved to be accurate reflections of the views held by President Kim Il Sung.

The two governments, divided by war and ideology for 35 years, are holding working-level talks to arrange a meeting between prime ministers to discuss unification.

In pressing for the talks since mid-January, the North has successively acceded to several positions held by the South. It has agreed to begin discussions between government authorities. Previously the North insisted it would sanction meetings of only political parties and social groups.

The North also has recognized the South by name as an independent government for the first time and has dropped its past insistence on signing a formal peace treaty with the United States before dealing with Seoul.

But each of those concessions involved ways of getting talks started and did not touch on what might come from the prime ministerial meetings. So far as could be learned, Pak's comments are the first North Korean indication of what scheduled it would accept for actually unifying the country.

"We favor first, multilateral cooperation and interchanges," Pak said. "Then, after such exchangtes, we envision a confederation of the North and the South while leaving social and economic systems intact on both sides. So the fundamental assumption is that neither side would try to impose its own system on the other side."

"The confederation," Pak added, "would last for a considerable time. And then this period will produce a better understanding between the two sides, and then there will finally be a consensus for complete integration."

The form that a unified Korea would take would be determined during the period of confederation, he said.

As examples of the first-stage series of cooperative arrangements, Pak cited the following:

Economic cooperation, including trade between the two countries is essential commodities. He said the North is willing first to begin selling iron ore to the South.

Joint diplomatic and cultural missions abroad.

Combined sports teams, such as the joint Olympic squad already suggested by Pyongyang and rejected by Seoul.

Military deescalation, including a reduction of forces, arms control, and a mutual pullback of troops along each side of the Demilitarized Zone that separates the countries.

Pak was reminded that the late president Park Chung Hee of South Korea has proposed beginning the unification process with economic agreements more than a year ago and that the North had rejected the idea.

He indicated that the North's attitude changed because Park is dead, victime of an assassination on Oct. 26.

"We knew that Park had no commitment to unification," he said. "He wanted a separate state, and his proposal would have led to creating two Koreas. He offered an economic interchange, but it was aimed at keeping two Koreas. He wanted to stay in power and to do so he had to post as a champion of unification. If we accepted it, it could only have been a help to him.

"We are ready to accept any proposal to the North-South unification if the other side has the commitment."

However, Pak emphasized that the North is not abandoning completely its hope holding what it now calls "broad-based" unification talks among political parties and social groups from both sides. The South rejects that idea as a device designed to weakened its position because it would bring into the discussion such anti-government personalities as former presidential candidate Kim Dae Jung. a

But Pak indicated the North is in no hurry to press its insistence on "broad-based" talks and is willing to let the official negotiations run for some time. For example, he said economic cooperation could be proposed and tested for an indefinite period before the other unofficial talks were held "if South Korean authorities show enough interest."

Pak dealt with the question of U.S. military forces in the South with an almost casual indifference, readily admitting that their presence would not interfere with the process of reaching a Korean accord. He said their withdrawl is "not necessary" to create the climate for agreement.

Some observers have felt that at some stage the North would revert to its former position of insisting on a total troop withdrawal. For more than a year, its stance on that point has been vague.

As an example of his country's new flexibility on that point, Pak pointed out the North had proposed a joint Olympic team for the Moscow Olympics at a time when more than 30,000 U.S. troops remain in the South and engage in joint exercises with South Korean forces.

"Of course," he added, "if the United States decides to help and gets out, that would be the best situation."