President Reagan is expected to tell West German Chancellor Helmut Schmidt today that failure of the allies to take a stronger stand against Moscow and Polish martial law authorities could produce a dangerous backlash in America that could seriously weaken the North Atlantic alliance, according to senior aides.

The chancellor's luncheon meeting here today with Reagan is being portrayed by these officials as probably the most important and toughest the German leader has ever had with an American president.

State Department officials said yesterday the administration is intent on not allowing the trouble in Poland to produce a crisis in the alliance. But other officials said the mood in the White House is that the time has come to talk bluntly and directly to Schmidt about the potentially grave consequences for the alliance if the European response to the repression in Poland continues to be perceived here as weak.

The president is not expected to threaten Schmidt, but rather to caution him that, as one aide put it, "public and political opinion in our country simply will not go on supporting an alliance where some of the key allies pursue business as usual with Moscow in these very special circumstances. People will begin to ask what does it mean for the common defense. How do Germans define at what point Soviet actions become intolerable? Do tanks have to come rolling across the border? If proxies such as the Polish army do the job, does that absolve the allies of any responsibility for taking action?" None of the North Atlantic Treaty Organization allies has thus far gone along with the Reagan administration's imposition of limited economic sanctions against Moscow. But West Germany's response to the crisis thus far, even in terms of verbal condemnation, is viewed here as the weakest of the major powers within the alliance.

Bonn also does not share the administration view that the crackdown in Poland was necessarily instigated by the Soviets, believing that it may well have been a Polish-inspired move meant precisely to avoid Soviet intervention.

Yet, West Germany is the key member of the alliance, especially in terms of influencing the Soviet Union and impressing Moscow with allied unity and seriousness. It is because of this central role for Bonn that today's meeting is described as so critical.

In effect, senior aides say, the meeting brings together the two central exponents of differing views on how to respond to Moscow in a potentially explosive situation.

Reagan views himself as having "a very clear-eyed view of the Soviet Union" and is convinced that the West helps Moscow repress the Poles when it fails to react and continues to trade. He is convinced that failure of the Europeans to join in a tough stand is a "prescription for acquiescence."

During National Security Council meetings here before Christmas, Reagan was said to be "the toughest one of the lot" among his top aides on Poland. He reportedly expressed the view that the crackdown was proof of the bankruptcy of communism and wondered aloud at the value of allies who were unresponsive to such a loss of freedom.

Chancellor Schmidt, on the other hand, is probably the leading statesman in Europe and also the most articulate spokesman warning about the danger of confrontation and the need for extreme caution in dealing with Moscow because the stakes are so high, especially for Europeans.

Although officials say they can't be sure exactly what Reagan will say to Schmidt, they leave no doubt of the effort to convince the chancellor how seriously the president views this crisis and the allied response.

"At the very least," one official said, "we want Schmidt to go away from here saying to himself that 'these SOB's are serious and we better consider that.' "

These officials acknowledge, however, that Schmidt and other European leaders have some justification, because of past experience, in not believing that American administrations are serious and consistent. The Europeans cite Reagan's earlier lifting of the Soviet grain embargo and other issues and ask why they should take huge risks with their trade and relations when the Americans may quickly change course.

Officials say that the White House understands and respects Schmidt's views and his political needs at home but that he will probably be told that "times are tough" and the United States would like to know at what point certain kinds of Soviet activity become intolerable.

"The Europeans," one U.S. official contends, "have become so adept at explaining away the bumps" in relations with Moscow "in the interest of detente that they no longer understand the strength and symbolism of taking stands on issues." If the allies took a stronger and more unified stand, the official claimed, the Soviets would not be able to try to split the alliance as they are now attempting by taking a very moderate tone with Bonn and a harsh tone with Washington.

Officials said that, on a sliding scale of expectations, the best thing that could come out of the Schmidt visit would be to lay the groundwork for a much more stringent and unified allied effort aimed especially at Moscow. While British, French and Italian support is also vital, officials say West Germany is the key because of its crucial position and power in Central Europe.

Officials hint that the administration may well ask the French, British and Italians, all of whom have been somewhat more expressive than the West Germans in verbally condemning the action in Poland, to take a tougher stand, which could leave the Germans looking like "the odd man out" in the NATO alliance. That kind of situation would be extremely difficult for Schmidt and the Germans.

Schmidt, on the other hand, has repeatedly tried to remind the allies that history makes it difficult for the Germans to give advice to or take sanctions against Poland.

Government officials say the United States would also like to see at least stronger words from Bonn, fewer statements that seem to equate Eastern and Western intervention, and a commitment for greater defense spending.

Officials also say that the possibility of trying to halt West European participation in the new gas pipeline from Russia is also still a lively topic in the White House and that some future U.S. economic measures could involve pressure on banks here to call in loans to the East because of the special crisis circumstances, a move that could have a potential ripple effect in West European financial circles.

Finally, though White House officials say nobody in the administration is talking about removing U.S. troops from Western Europe, officials say they believe there is a real danger that Congress, if it perceives that the Europeans won't challenge Moscow under any circumstances, could once again begin action to bring home the troops.

Last month, well before the Polish crisis, the U.S. ambassador to Bonn, Arthur F. Burns, told a West German audience that the 350,000 American soldiers in Europe would not stay there "if they are not welcome." Burns' remarks were aimed at the spreading anti-war demonstrations against U.S. missiles in Europe. Yesterday, officials mentioned the Burns speech again, which suggests that Schmidt could hear the same thoughts from the president.