he defense leaders of all Soviet Bloc countries have gathered in the Soviet Union to observe large-scale Soviet military maneuvers now underway near the borders of Poland, the news agency Tass said today.

The surprise announcement came shortly before Tass made another harsh attack on Poland's independent trade union, Solidarity, and described the union's congress at Gdansk as a demonstration of Solidarity's intent to seize political power.

Polish Premier Wojciech Jaruzelski, who also holds the defense portfolio, was listed by Tass as being among the nine allied military leaders at the headquarters of Marshal Dmitri Ustinov, the Soviet defense minister, who is in charge of the war games.

Others are the defense ministers of East Germany, Czechoslovakia, Hungary, Romania, Cuba, Vietnam and Mongolia, and the first deputy defense minister and chief of the general staff of Bulgaria.

The gathering at an unspecified location in Byelorussia was described by Western diplomats here as highly unusual, and presumably called for consultations about the crisis in Poland and broader military problems caused by President Reagan's defense policies.

Jaruzelski and Polish Communist Party leader Stanislaw Kania were last here a month ago for talks with Soviet President Leonid Brezhnev.

Since then, however, the situation in Poland has deteriorated, and the Soviet press has renewed its pressure on the Polish Communist leadership to toughen its opposition to Solidarity. The current military maneuvers are regarded by foreign observers as a further attempt to bring home to the Polish people the Soviet dislike of what is happening in Poland.

Tass, in its first substantive comment on the Solidarity congress since it began Saturday, said today that reports and speeches had concentrated on attacking the Polish Communist Party, the political system and Poland's achievements under socialism.

As before, Tass continued, Solidarity does not offer any constructive program for solutions of Poland's problems.

"At the same time," Tass said, "ever-new demands to the state, including material demands, are being irresponsibly formulated although it is clear that there are no resources and conditions to meet such demands. Judging by everything, the creation of an impasse is exactly what suits the managers of the congress because they are aiming at seizing political power in Poland and would like to undermine the faith of working people in the socialist people's state."

Tass also appeared to be raising the question of the legitimacy of the congress by suggesting that most of its delegates did not speak for Polish working people.

Under the headline "Whom do they represent?" the agency asserted that "89 percent of all delegates are salaried employes of the Solidarity apparatus." It then quoted a Solidarity spokesman, M. Podgurcyk, as saying that "workers comprise less than 25 percent of the delegates."

The commentary appeared to have been written before the Solidarity congress adopted several resolutions later today, and was regarded as a reaction to claims made earlier at Gdansk that the union's leadership had in effect become the national parliament.

Virtually all aspects of the congress have already been denounced by the Soviets as contradicting the principles of Marxism and Leninism, and today's call by Solidarity for the establishment of independent trade unions in Eastern Europe and the Soviet Union is expected to make things much worse.

Eastern European sources here said that however provocative these resolutions may appear to be to Moscow, it is unlikely that they will snap the Kremlin's patience. But they said that Jaruzelski probably will come under increasing pressure here to take strong measures against the independent union.

Today, news reports on the war games told of small-scale tactical exercises in various parts of Byelorussia, Latvia, Lithuania and Estonia in preparation for a major mock battle later this week.

Soviet television showed amphibious exercises on the Baltic Sea, with landing craft disgorging tanks and other heavy equipment. Eight troop landing ships, an aircraft carrier, a helicopter carrier, a cruiser, two destroyers and a frigate are among about 80 vessels assembled off the Soviet coast in the Baltic.

Polish television said that Polish and Soviet tank units were holding joint exercises in southwestern Poland, the Associated Press reported from Warsaw.

This is not the first time the Soviets have used the implicit threat of military intervention to warn the Poles that the limits of what the Kremlin considers acceptable were being reached. Since the Polish crisis developed more than a year ago, however, Moscow's objectives have undergone considerable change and now have been scaled down to two major goals: the preservation of Soviet security interests and of the Polish Communist Party's control of the country.

Yet, while it was torn between ideology and painful pragmatism, the Kremlin had gradually faced up to Polish reality. Various Soviet and Polish sources reported that Moscow had come to terms with the inevitablity of liberalization in Poland, along with its free trade unions and economic reforms, as long as the country remained within the socialist framework.

Events in Poland, however, are now widely regarded as having gone beyond efforts to liberalize the existing system and have made Poland a special case in Eastern Europe--another Hungary or Yugoslavia.

Within Poland, the Soviets, by their own pronouncements, now see an open struggle for political power in which Solidarity, by using the strike weapon and other pressures, is perceived to be seeking to overthrow the Communist Party by destroying the economic and social foundations of socialism.

Outside Poland, the Soviets see a hostile Reagan administration conniving with the Polish-born pope, John Paul II, in an effort to undermine the Warsaw Pact. Such Soviet fears are fueled by statements attributed to various Polish church sources about the pope's desire to see the neutralization of his native land.

In this context, according to Eastern European sources, the present Soviet war games should be seen as an explicit reminder that the option of intervention remains open if the Poles should create a major security problem for Moscow.

The Soviets are seen as continuing to hope that the Polish communist leadership will manage to bring the situation under control and terminate the endless controversies and confrontations that have set the country's economy on a downward slide.