Two underground leaders of Poland's suspended Solidarity trade union have said that they want a compromise with the martial law authorities but are ready for a long and bitter struggle if their organization is banned.

The two officials, both members of Solidarity's four-man provisional leadership, which is coordinating resistance to martial law, said in written responses to questions, that the union had managed to regroup and reorganize itself in the five months since its suspension. They appealed for continued Western pressure against Poland's military government, describing the pressure as a powerful stimulus to liberalization.

The Washington Post submitted questions through intermediaries last month to Zbigniew Bujak and Wladyslaw Frasyniuk, chairmen of Solidarity's Warsaw and Wroclaw branches respectively. Their responses give an insight into the thinking of the Solidarity leaders who escaped arrest on the night of Dec. 13 last year and have since been in hiding. Both aged 27, the two men are typical of the educated worker activists who rose to prominence following strikes in August 1980 that gave birth to Solidarity.

The two men have been in contact with each other from their hideouts and last month organized a secret meeting of Solidarity leaders from all over Poland. The meeting formally established a provisional coordinating commission to run the union's affairs.

The authority of this new body will be tested Thursday when it has called for a 15-minute "warning" strike in all Polish factories to protest five months of martial law.

Referring to the setting up of the commission, Frasyniuk said that the first meeting had taken place at "very great risk" to those involved. He said the participants had acknowledged the need to coordinate protest actions on a nationwide basis following a period during which the government successfully interrupted communications between different Solidarity chapters.

Both Frasyniuk and Bujak addressed themselves to the major problem of how Solidarity would react if, as many of its members expect, it is formally outlawed. When martial law was first introduced, trade unions were suspended but not banned, and their future status was left unclear.

Bujak described Solidarity as "a social movement still in its infancy." He said people were waiting to see whether it would be possible to restore independent unions. If such unions were banned, he predicted that most workers would join an informal and illegal Solidarity.

He said that, while he himself could only support nonviolent forms of protest, any attempt to crush Solidarity could result in the formation of an urban guerrilla movement.

Frasyniuk was more specific. He said that a ban on Solidarity could only be regarded as a refusal by the authorities to reach agreement with Polish society as a whole and should be countered by calling for a nationwide general strike. But, like Bujak, he supported a policy of negotiation with the government and "far-reaching concessions" on both sides.

"We are not madmen. We support a compromise. But society's representative in such a compromise can only be a strong, consolidated workers' organization. We are trying to restore such an organization following last December's attack by the government," Frasyniuk said.

Bujak said Solidarity had reduced its conditions for opening talks with the government to what he called "a minimum:" the freeing of internees and an amnesty for people found guilty of crimes under martial law. The government, however, has refused so far to negotiate formally with the old Solidarity presidium under Lech Walesa, which it has described as being made up of "political extremists."

Both Solidarity leaders said that they had had no contact with Walesa since the declaration of martial law and were working on their own. Frasyniuk added, however, that "I interpret his Walesa's silent resistance to the authorities as eloquent enough for me to know what he would like us to do."

The interview also illustrated some of the differences in outlook between Bujak and Frasyniuk. According to Solidarity sources, Frasyniuk has much tighter control over his rank-and-file than Bujak, who devotes more of his time to thinking about long-range strategy. The Wroclaw branch of Solidarity, which Frasyniuk has headed since February 1981, is reputed to be the best organized in the country.

Bujak, a former engineer at the Ursus tractor plant in Warsaw, admitted in the interview that he had little contact with ordinary workers. He said his present situation made it difficult for him to learn the moods and opinions of Solidarity members and suggested that each factory should set up its own clandestine union cells.

"Dec. 13 proved that an organization should not be based merely on the charisma of its leaders as they can be removed very easily. Under autocratic systems, of course, people are used to obeying orders and instructions rather than to taking decisions of their own. The situation in the factories, however, seems to show that workers are getting through this difficult period. They're organizing themselves and will be ready not merely to act on the orders of leaders like me but, much more important, produce their own leaders," Bujak commented.

Frasyniuk, by contrast, said he had set up a regional strike committee for lower Silesia in close touch with all big factories in the Wroclaw area. A former bus driver, he said he believed that workers in the region were prepared to undertake protests in response to specific appeals.

He said that in some Wroclaw factories workers were engaging in passive resistance, even though this frequently resulted in significantly lower earnings. He cited the example of a chemical company, Chemitex, where because of inefficient work wages had fallen to an average of 1,800 zlotys ($24) a month.

Frasyniuk said the main tasks of Wroclaw regional organization were to give assistance to the families of repressed Solidarity activists, spread information, organize protest actions, and prepare for a general strike should it become necessary.

Frasyniuk's special position in Wroclaw stems in part from his actions during the first hours of martial law.

He had attended a meeting of the union's national commission in Gdansk, but left shortly before the mass arrests of Solidarity leaders.

He said in the interview that, on the train going south to Wroclaw, he and several of his colleagues were warned that the police were waiting for them at the station. The railmen stopped the train and he went into the city on foot where he immediately set up a unified strike committee, first at the bus station and then, after the strike had been "pacified," at other big plants.

Bujak, too, had been attending the Solidarity meeting in Gdansk. From the railway station there, he said, he saw the police arresting union leaders at the Monopol Hotel. He then hid in Gdansk for a week before being smuggled to Warsaw "with the assistance of the railmen."

Both leaders insisted that it was impossible to compare the situation in Poland today with the period before August 1980 when Solidarity was formed.

"Before 1980, there were just several thousand opposition activists in the entire country. At the moment, the numbers of active Solidarity members run into hunderds of thousands. The experience from the struggle against totalitarian rule has a cumulative effect," Bujak remarked.

Frasyniuk commented: "Sixteen months of freedom divide us from the pre-Solidarity period. During this time, society learned how to organize itself and understood its power. Everybody now understands the goal of our struggle, and this consciousness is impossible to destroy."

Asked about Western reaction to martial law, Bujak said he believed that economic sanctions were a much more effective method of forcing the Polish authorities to reach an agreement with Solidarity than passive resistance within Poland itself. But he said the situation could change as Polish industry developed closer ties with the Soviet Bloc and became less dependent on Western imports.

Bujak appealed for technical assistance from Solidarity sympathizers in the West, including low-cost duplicating machines and shortwave radio sets.

Frasyniuk said Western pressure on the martial law authorities could help create a climate for internal reforms in Poland.

He also asked for more medical assistance, saying that children were undernourished. He said there was a desperate need for "medical equipment, drugs and feeding mixtures."

Both men look back at the past with a feeling that what happened last December was inevitable. In Bujak's opinion, Solidarity was faced with a choice of severely restricting its activities or coming into conflict with the Communist Party. If it had chosen the first course, it would have lost its independent identity, he said.

"Besides, we were simply convinced that it was impossible for the Army to be used by the authorities against society," he said.

Frasyniuk said that Solidarity leaders had been unable to contain the pressure of demands from below. Attempts to rein in the rank-and-file were regarded as "selling out" to the authorities.

"We presidium members were so busy trying to calm down the multiplication of grievances, which we now know were provoked by the authorities, that we simply did not have time to spot a threat to the union. That was our biggest mistake: a failure to see what the authorities were up to."

Bujak, however, said that the relative ease with which martial law was introduced could work in Solidarity's favor.

He said he believes that the authorities were prepared to use much greater force to crush resistance.

"The way it turned out, we were able to avoid losing our most courageous and determined activists at the begining of this war. They are now working underground, using other methods, and thus in my opinion the long-term chances of reactivating Solidarity are much greater."