This dispatch is based on information arriving from Poland:

Solidarity leader Lech Walesa, who has been held under house arrest since martial law was declared Dec. 13, has laid down conditions for beginning negotiations with the Polish government, including insistence that the talks be held on neutral ground and that the rest of the 18-member Solidarity presidium and three union advisers be present, according to knowledgeable sources in Warsaw.

The government and Solidarity officials have held lower-level contacts, union sources said, but little progress was reported. There have been at least three meetings between Stanislaw Ciosek, the government minister in charge of trade union affairs, and Stanislaw Rusinek, a member of the leadership of Solidarity's Warsaw regional organization.

Meanwhile, a high-level Communist Party source said that the martial-law government is being run by a "mixed group" of generals and top party leaders who meet often and informally to make all key decisions. The source said that the government was a hybrid in which neither the party nor the military had superior decision-making power.

"It's not a military coup," said the source, who has access to restricted information at the headquarters of the Central Committee and who insisted on anonymity. "But at the same time the military is not just acting as an instrument of the party. It's somewhere in between."

The official did not provide the names of the members of the unofficial ruling group. But in addition to the martial-law leader, Gen. Wojciech Jaruzelski, and his deputy, Gen. Florian Siwicki, the official said it included Politburo members Kazimierz Barcikowski, Stefan Olszowski and Deputy Premier Mieczyslaw Rakowski. The latter three represent three distinct factions within the Communist Party and reportedly have been charged by Jaruzelski with drawing up plans for a political solution to the Polish crisis.

Radio Warsaw reported that the military government had fired about 90 important officials throughout the country. The announcement of the firings appeared to be part of government efforts to cast the takeover as a crackdown against corrupt officials of the Communist government as well as against Solidarity.

The appearance of an increasing number of underground Solidarity publications, some of them mimeographed with a distinctive logo on the masthead, indicates that remnants of the suspended union are mobilizing after a period of stunned inactivity.

The Communist Party source said that he expects the emergence of an underground resistance movement against the martial-law government. He said the key question is whether it would confine itself to "peaceful" activities such as distributing leaflets or would turn into a terrorist organization.

The former, he said, could be handled easily by the authorities, but the latter would provoke what he called a severe "counterreaction."

In Moscow, the Communist Party daily Pravda reported that Polish soldiers were fulfilling martial-law duties with great loyalty and a growing number of them were applying to join the Polish party.

The paper also suggested that Washington had failed to win support for its economic sanctions against the Soviets in connection with the Polish crisis and was blackmailing its allies by threatening to cancel arms control talks.

Radio Warsaw reported that talks last week in West Germany between West German Foreign Minister Hans-Dietrich Genscher and Deputy Premier Rakowski "should be assessed positively," and praised the "realistic position" of the West Germans in declining to support U.S. economic sanctions against Poland. The report said Rakowski had "emphasized that the state of martial law is not to be equated with a military dictatorship."

Canadian Foreign Minister Mark MacGuigan said in Windsor that Canada is considering introducing its own sanctions against the Soviet Union as a result of the imposition of martial law in Poland, The Associated Press reported Saturday. "We haven't taken any steps as such," MacGuigan said in an interview Friday. "We haven't yet made any sanctions, but we are considering the subject."

Canada originally indicated that it would not support the sanctions against Poland or the Soviets, but MacGuigan said he told the Reagan administration that Canada will not undermine U.S. measures against the Soviets, including a ban on high-technology sales and the closure of U.S. airports and harbors to Soviet traffic.

In Warsaw, the Communist Party source also said that there have been two additional deaths as a result of martial law. The government has acknowledged seven striking miners were killed in Silesia during a clash with security forces and that another man died after being wounded in street fighting in Gdansk.

One of the additional deaths, the source said, was a police officer who was killed in fighting Dec. 16 at the Wujek coal mine in Katowice, where the seven miners died.

The other previously unreported death, the official said, was a man who suffered a heart attack during the suppression of a strike at Wroclaw Polytechnic University.

In this official's account of the Wujek fighting, 41 police officers and soldiers were injured when miners disabled a tank that had attempted to break down a barricade at the main gate. As security forces fought hand-to-hand with miners using chains and other crude implements, he said, one police officer panicked and opened fire with a machine gun.

Meanwhile, Radio Warsaw reported that a Katowice court in summary proceedings sentenced nine Solidarity officials to prison terms up to seven years for continuing union activities after declaration of martial law. Five of the leaders were charged with leading a strike at the Huta Katowice steel complex.

The broadcast, monitored in Vienna, said the five were found guilty of continuing Solidarity's activities, staging the strike and doing great damage to the national economy.

In developments relating to the economy, the government announced the devaluation of the national currency, the zloty, from 34 to 80 to the dollar in a move that appeared to be aimed at curbing speculation and black-marketeering.

Radio Warsaw, in an announcement describing pay levels for idle workers in factories that are not operating at full capacity, reported yesterday that "a shortage of fuel, energy and raw materials is causing standstills in various enterprises and works."

In a separate broadcast, the radio described efficient road and rail transport of food arriving from the Soviet Union.

"In the first days of the new year," the broadcast said, "the railway stations of Geniusze and Siemionowka in Bialystok Province have received 6,000 tons of rice from the Soviet Union.

"Large amounts of gasoline are also being received at the Bialystok region dry ports . . . . Cotton and other goods are also being received."

The radio said that "transloading work continued" in the Baltic seaports "on the first day of the new year, mainly on vessels carrying foodstuffs. Twenty-three vessels, 20 of them flying the Polish flag, are moored in Gdansk port, while in Gdynia port the number of moored vessels is 33."

As the government approaches another test of normalcy with the scheduled post-holiday reopening of a number of factories Monday, a Solidarity publication dated Dec. 30 said that about 20 factories have not been operating normally. Among them is the Lenin Shipyard in Gdansk, where three previous attempts at reopening have failed and authorities have been issuing new work cards in an apparent attempt to weed out troublemakers.

Another center of persistent resistance has been in the western industrial city of Wroclaw, where the Pafawag railroad car factory is a focus of worker anger. It has been the scene of intermittent strikes, and security forces have forcibly put down demonstrations and made numerous arrests.

A Wroclaw newspaper charged yesterday that Solidarity leaders in the city of Bielsko-Biala had been paid for organizing strikes. The newspaper published what it said were copies of receipts paid to Solidarity activists, but it did not say who had made the alleged payments.

Western sources said that in response to questions from Western diplomats concerning individual detainees, Polish officials hinted that they might consider sending some of them to the countries that had expressed concern about their fate.

There was some doubt about the seriousness of the Polish officials' offer. One diplomat characterized the Polish stance as a "rhetorical flourish."