West German Chancellor Helmut Schmidt, under pressure from the Reagan administration, for the first time yesterday joined the president in publicly charging Moscow with "responsibility" for the crisis in Poland.

Schmidt's agreement to the joint statement is viewed by the White House as the most significant gain to come out of the two leaders' meeting here.

The Reagan administration has been seeking stronger verbal condemnations and actions against both the Soviets and the martial law authorities in Poland from the allies, especially from West Germany as the key European power in NATO. The administration believes that allied unity is essential on this point to bring pressure on Moscow to ease the situation in Poland.

While none of the allies thus far has joined in the limited and specific economic sanctions against the communist authorities announced by Reagan, Schmidt, until yesterday, had also refrained from specifically linking the Soviet government to the crackdown by the Polish security forces. That omission is known to have annoyed the White House.

In the statement, the two leaders "noted the responsibility of the Soviet Union for developments in Poland and expressed concern about the serious pressure it is bringing to bear against Polish efforts for renewal. They insist Poland be allowed to resolve its problems without external interference."

At a press conference later, the chancellor was asked what had changed his mind about talking about the Soviet role. Schmidt responded that the question gave him an opportunity to "get out of this mess that has been fabricated."

He said the "German government hasn't changed its judgment at all." He pointed to his speech in the parliament on Dec. 18 and a parliamentary resolution on Poland the same day which "defined the same elements which you will find today in the joint release" with President Reagan.

Actually, neither of those documents contains any reference to the Soviet Union with respect to Poland.

The documents lay out the basic German position of calling for the lifting of martial law, freeing of those arrested, and negotiations involving Polish authorities, the Catholic church and the Solidarity trade union. The parliamentary action, which was initiated by the political parties and not by Schmidt, also calls for holding future official economic aid in abeyance while the repression continues.

Bonn's first public linking of Moscow and the Polish crisis took place Monday in Brussels, but only when foreign ministers of all 10 European Economic Community members put their names to a statement denouncing Soviet pressure on Poland.

Administration officials said privately yesterday that while the issuance of a joint statement was a West German idea, the language on the Soviets was put in by the administration and agreed to by Bonn.

The Germans traditionally are wary of provoking the Soviets, who have overwhelming military strength, a big trade business with Bonn and control over East Germany.

Bonn officials also had previously expressed the view that they did not agree with the United States that the Soviets had instigated the Polish crackdown. Yesterday Schmidt said it didn't really make much difference if the Polish authorities acted because of the imminent threat of Soviet forces being used or because of Soviet pressure on the Poles to act.

In their joint statement, Schmidt and Reagan said they "agreed on their analysis of the Polish situation" and that the crisis "demonstrates once again the obvious inability of the communist system to accept those changes necessary to meet the legitimate aspirations of their peoples."

Both leaders, as is customary, pledged themselves to the "close and trusting" relationship between the two countries and obviously sought to keep any disputes over Poland private in order not to publicly wound the alliance.

But the joint statement also contained an unusual agreement, which might reflect a recognition that crucial issues of alliance unity are at stake, to set up very high-level "coordinators" for American-German relations. The U.S. coordinator will be Assistant Secretary of State Lawrence S. Eagleburger and his German counterpart is Minister of State Hildegard Hamm-Bruecher.

Earlier in the day, immediately after their 2 1/2-hour meeting and working lunch at the White House, Reagan and Schmidt came out on the South Lawn, where the president made a very strong statement on Poland.

Reagan talked of "the need for forceful western measures" to get both the Soviets and Poles to lift the siege and start a dialogue for reform. He said he emphasized to Schmidt his belief that "a tangible alliance response to the Polish crisis must be made now" and that "should we fail to insist that the Soviet Union stop pressuring Poland directly or indirectly, the gravest consequences for international relations could ensue."

The president did not say publicly what that response should be. But U.S. officials later emphasized that they were pleased with the subsequent joint statement which contained not only the remarks about the Soviets but also a pledge that Bonn, along with its European partners, will look into decisions regarding economic moves which "best serve their common objectives" and avoid undercutting U.S. actions.

Reagan also said he made clear the need to reach out to public opinion in both countries, especially among the younger generation, to tell them that NATO is the one instrument that has kept the peace for more than 30 years.

In their private meetings, Reagan is also said to have told the chancellor of his concerns about public and congressional opinion in the United States if the allied response to Poland continues to be perceived here as weak. The president also reportedly brushed aside a suggestion by one German official that U.S. domestic concerns on Poland were fueled by the large Polish-American population.

As Schmidt's motorcade pulled up to the White House yesterday morning, a group of about 150 Polish-Americans paraded in front of the gates, waving Polish flags and carrying banners calling on West Germany not to trade human rights for a Soviet gas pipeline.

Officials here described the private meetings as not confrontational, with Reagan making points about U.S. actions and concerns but Schmidt doing most of the talking about other matters such as economics and arms control.