Poland's military leader, Gen. Wojciech Jaruzelski, announced tonight that "the main rigors" of martial law will be suspended by the end of this year and indicated that many Poles interned for political reasons will be released soon.

In a televised address on the eve of the anniversary of the sudden imposition of martial law a year ago, Jaruzelski called today's move a major step toward full lifting of martial law, "which we want to see happen in as short a time as possible."

But he made clear that the Army would continue to play a significant political role in Poland, even though its presence inside factories and other institutions will be reduced. He said a limited amnesty would be considered for persons convicted of crimes under martial law.

The plan outlined by Jaruzelski amounted to a gradual phasing out of martial law rather than its sudden abolition. He made clear that the Military Council of National Salvation, of which he is chairman, will not be abolished but that its function will change from "administering" martial law to "guaranteeing" a secure transition to civilian rule.

The measures fell short of lifting martial law altogether as had been suggested by official leaks to Western governments and journalists during the past month. This could reflect the disappointment of the Polish authorities at the lack of any concrete Western promise to respond by ending economic sanctions.

State Department and White House officials had no immediate comment, referring reporters to remarks made by President Reagan Friday during the signing of a proclamation on human rights, in which he spelled out conditions for restoring normal relations with Warsaw, United Press International reported.

["I repeat, if the Polish government introduces meaningful liberalizing measures, we will take equally significant and concrete actions of our own," Reagan said Friday. "However, it will require the end of martial law, the release of political prisoners and the beginning of a dialogue with truly representative forces of the Polish nation, such as the church and the freely formed trade unions to make it possible for us to lift all the sanctions."]

Jaruzelski's speech came on the eve of the anniversary of his military crackdown last year that led to the suppression of the independent Solidarity trade union and the suspension of many civil rights. He said that further details about providing the government with "emergency powers" over a transitional period would be revealed Monday at the start of a two-day debate in the Sejm, the national legislature.

Dressed in full military uniform, Jaruzelski told television viewers: "I promise you that anarchy will not be allowed to reappear in Poland. Let nobody within the country or abroad believe for one moment that the present decisions will make possible a second phase of anarchy."

Political analysts here believe that the Army will continue to play a prominent role even after the full phasing out of martial law. Jaruzelski is Communist Party leader and premier as well as minister of defense and has placed his subordinates in key positions in government and the economy.

Leaving open the possibility that some workers would remain under military discipline, Jaruzelski said that the number of Army commissars would be reduced, leaving them only in "key sectors." Under martial law, the commissars were given powers to issue orders to workers as in the Army.

Jaruzelski explained his cautious approach to the lifting of martial law by saying that opponents to communist rule in Poland were still active. He said internment would not be "applied any more," but added that it was necessary to maintain for a temporary period "those restrictions that directly defend the interests of the state, protect the economy, and strengthen the security of its citizens."

Promising that "the main rigors of martial law will stop functioning by the end of the year," he said: "This will be a very important step to the full lifting of martial law, which we want to see happen in as short a time as possible. But we cannot just jump into a full normalization of life. We have to approach it step by step."

In practice, the abolition of internment is likely to mean the freeing of most of the leading Solidarity activists and advisers who remain in detention. Those likely to benefit include prominent Roman Catholic intellectuals such as Boleslaw Geremek and Tadeusz Mazowiecki and workers leaders such as Andrzej Gwiazda and Jan Rulewski. Lech Walesa, the former Solidarity chairman, was released last month. Under martial law, internment is a category of detention used when no specific charge is made.

Edward Gierek, the former Polish Communist Party leader interned with other discredited officials when martial law was imposed a year ago, presumably also will be freed now.

However, several thousand Solidarity activists convicted of illegal union activity under martial law or awaiting trial will remain in detention. So will several members of the dissident Committee for Social Self-Defense, known as KOR, such as Jacek Kuron and Adam Michnik, who have been charged formally with attempting to overthrow the state.

Jaruzelski made clear that there would be no unconditional freeing of all political prisoners, as demanded by Reagan, by talking of a possible "amnesty within a socially useful degree." He did not say when it would be introduced.

In a letter to Jaruzelski made public yesterday, Walesa said a full amnesty and the reinstatement of workers dismissed for political reasons were essential for social peace in Poland. He also called for workers to be allowed freedom to choose among different trade unions, which was one of the basic principles of the labor agreement signed in Gdansk in August 1980 that the government has said it will respect.

Jaruzelski ignored Walesa's letter in his television broadcast and did not directly address the issues raised in it. The official position is that, following Solidarity's legal dissolution in October, Walesa is merely a private citizen.

Describing what he called the achievements of a year of martial law, Jaruzelski said that "positive tendencies" in the Polish economy and obedience of the law had been strengthened.

Jaruzelski's appearance on television tonight came almost as an anticlimax after mounting speculation of a complete end to martial law -- and contrasted with his dramatic broadcast at dawn on Dec. 13, 1981, when he announced the military takeover. That night thousands of Solidarity activists were arrested. A wave of protests erupted around the country, but one factory after another was stormed by security police.

Tonight, Jaruzelski repeated what have now become standard accusations of Western meddling in Polish affairs and warned that "appropriate" countermeasures were being considered.