Poland's leader, Gen. Wojciech Jaruzelski, warned Solidarity supporters today that nationwide street demonstrations planned for Tuesday would not be tolerated and hinted that major unrest could delay the lifting of martial law.

His speech to Army officers at a graduation ceremony in the western city of Poznan was part of an intensive official campaign, including the stepping up of security measures in Warsaw and other major cities, to dissuade workers from taking part in the rallies.

Underground leaders of the suspended Solidarity union have called the demonstrations to commemorate the anniversary of the Gdansk agreement of Aug. 31, 1980, that legalized independent trade unions.

Another sign of the authorities' unease was an official warning issued to Western correspondents based here to maintain strict accuracy and "objectivity" during the coming days. Journalists were summoned to the Foreign Ministry to hear a communique read by an official threatening "the most far-reaching consequences" if they filed dispatches deemed untruthful or exaggerated by the authorities. This was presumed to mean that they would be expelled.

The collective warning, the first of its kind since the imposition of martial law in December, followed a series of official complaints accusing individual correspondents based here of presenting a distorted picture of events in Poland. So far, however, no Western journalist has been expelled, which seems to reflect the continued wish of the Polish authorities to maintain ties with the West.

In his speech, which was restrained in tone in comparison with other official statements during the past week, Jaruzelski said that the government still intended to lift martial law by the end of the year but that the real decision would depend on society.

"Let people deprived of common sense not push Poland back once again," he said. "Let August 31 not be marred by excesses and irresponsible demonstrations, but let it be remembered through peace, effort and work. Someone may or may not like martial law, but it is the law and it must be respected. Breaking it will not be tolerated."

Jaruzelski, who is Communist Party leader and prime minister in addition to chief martial-law administrator, promised to continue with political and economic reforms contained in the Gdansk agreement. He said the Army could help to implement the reforms by strengthening respect for the state.

"Only a strong and stable state is capable of reform. When it is weak, preoccupied with conflicts, it loses its will. Whoever acts today against the interests of the state is dragging Poland backward and putting a brake on the process of change," he declared.

Jaruzelski's aides have argued privately that next week's rallies -- if they take place -- could strengthen the hand of hard-liners within the Communist Party who are opposed to reform. The opposite view is taken by underground Solidarity activists who say that a show of strength by union members will force the government to negotiate with Solidarity's interned leader, Lech Walesa, and the Roman Catholic Church.

The church has supported government appeals for calm, but it also has demanded a reopening of the dialogue between the authorities and society. A pastoral letter from Polish bishops read in churches throughout the country today said that "feelings of rebellion and anger, disappointment and depression, are stirring in the hearts of many Poles." It described the "abyss between government and governed" as getting "deeper and deeper."

The bishops said that the Gdansk agreement could still provide a basis for national understanding.

"We appeal to everybody to celebrate this anniversary in a spirit of seriousness and peace," the statement said. "It would be a great evil and disaster if the anniversary of the social agreements was used by anybody for violent clashes or fraternal bloodshed."

The military authorities are seeking to dissuade workers from participating in the demonstrations through warnings of severe punishment under martial-law regulations. A statement issued by the prosecutor's office today said that 27 people were arrested yesterday for distributing illegal leaflets calling for protests and would be brought before special military courts.