On the eve of a crucial Communist Party congress in Poland, some senior officials in the Reagan administration are attempting to initiate new support for that nation's precarious experiment in democratization.

But it is not any threat of Soviet military intervention that preoccupies American policymakers. Instead, what is unfolding today in Washington as a counterpoint to what is unfolding in Poland is literally at the "chicken feed" level.

Several senior administration officials are scheduled to discuss one of Poland's most tangible needs -- more food -- with a congressman never ranked anywhere near the center of geopolitical thought: Edward J. Derwinski, a burly, conservative Republican representative from Illinois' 4th Congressional District.

Derwinski is noted in and outside his home base in Cook County for loud sports coats, a dry wit, fluent Polish and ardent Roman Catholicism, as well as his positions as ranking Republican on the House Post Office and Civil Service Committee and second-ranking Republican on the House Foreign Affairs Committee.When John Paul II became the first pope to visit the White House in 1979, Derwinski, then-Sen. Edmund S. Muskie (D-Maine) and House Foreign Affairs Committee Chairman Clement J. Zablocki (D-Wis.) were an impromptu trio on the South Lawn, singing, in Polish, "Sto Lat" -- live a hundred years.

Now Derwinski is a leading figure in determining whether Poland will receive in the next few months about 400,000 tons of American corn, worth about $80 million, to feed chickens that it otherwise would have to slaughter in huge numbers. This issue, Derwinski maintains -- and many State Department specialists agree -- will be construed in Poland as a new signal of U.S. willingness or unwillingness to help Poland's reformers, as one senior official put it, "keep their experiment alive."

The Reagan administration is divided internally about how far the United States, given its preoccupation with budget cuts and economic austerity, should go toward bailing out Poland from its undisputed economic chaos.

"I think that in the last analysis the political reality is that we will do what we have to in order to encourage the evolution of democracy in Poland and to discourage Soviet intervention," one senior U.S. official said last week. But he added, "I think it is going to be a very tough battle" inside the Reagan government to obtain any large sums in light of the domestic imperatives.

For the rest of this year, this official projected, "we will ad hoc it." The real test will come next year -- if Poland's reformist drive survives the special Communist Party Congress starting tomorrow and the Solidarity congress in late August or early September. Solidarity is the force that began as a labor campaign to establish free trade unions and has turned into a mass movement to liberalize all Polish institutions.

At present, the issue facing the Reagan administration is of smaller but nevertheless troubling dimensions.

Derwinski, who has been visiting Poland for 20 years, made a trip last month in which he talked with Poland's leading figures in the role of President Reagan's representative at the Poznan trade fair. Aboard Reagan's plane on a trip to Chicago late Tuesday, Derwinski raised with Agriculture Secretary John R. Block the subject of new emergency food aid. Derwinski said Block promised to explore the issue.

Next, Derwinski arranged meetings to be held today with Lawrence S. Eagleburger, assistant secretary of state for European affairs, and Richard E. Pipes, National Security Council staff specialist on the Soviet Union and Eastern Europe. Both are sensitive to the Polish situation and its repercussions on East-West relations; Pipes was born in Poland and Eagleburger was formerly ambassador to Yugoslavia.

In a letter to Reagan, Derwinski wrote that Poland urgently requires "400,000 tons of corn for chicken feed" which he recommended should be sent under credit provisions of the Agriculture Department's Commodity Credit Corp. Poland needs the feed, he wrote, "for delivery starting late in August or they must slaughter hugh numbers of chickens and further aggravate their continuing problem of food shortages."

Administration officials say it is unclear whether legislation will be required to provide Poland with the $80 million in new U.S. grain that it seeks. Derwinski says it should be possible to arrange the new grain loan through the Commodity Credit Corp., but officials there say they have no existing authority to provide the corn, for which Poland has no money to pay.

Poland last year received $670 million in American agricultural credits for a three-year term through the CCC, but it has yet to draw about $100 million of that amount, officials said. It cannot use that credit to purchase the corn to feed its chickens because it cannot come up with the $20 million in cash it would need to invoke all the credits.

The CCC program provides government guarantees of the principal of bank loans, plus 6 percent interest. But the going rate of American interest is about 20 percent, and Poland has to pay the difference -- thus the need for the $20 million that Poland says it doesn't have.

CCC officials also note that U.S. agriculture credits for Poland last year amounted to one-third of CCC's credits worldwide, in a program that is "a commercial tool -- not an aid program." As a Communist nation, Poland is ineligible for other forms of agricultural aid.

CCC's protestations mean little to Derwinski, who voices his perceptions of the Polish situation in language that diplomats, sensitive to the bitter hostility between Moscow and Peking, would hardly use in public -- even though many share the perceptions.

Derwinski said publicly on June 17 that what is happening in Poland "is being called the death of communism in Eastern Europe." Derwinski said he rejected that description so far as Poland is concerned, "because in Poland, communism never had any roots."

His assertion that events in Poland attest to "the rejection of communism" was seized upon in the Eastern European press as added evidence that the United States, as Reagan has said on several recent occasions, is looking forward to the crumbling of Communist rule throughout Europe.

Derwinski said he is telling administration officials the Soviet Union now surely recognizes that if it does invade Poland "it will inherit only chaos."

"My gut feeling is that they [Soviet planners] have analyzed the situation and decided that the time to move was last fall," he said. "Not having moved then, they can't move now because the Polish government has made so many adjustments to satisfy the Soviet Union" that Poland is making no attempt to break out of the Soviet bloc.

The "technocrats" in Poland, "as opposed to the party stalwarts," Derwinski said, "would like to see the facade of the party structure remain, but they would like to do the rational thing up and down" to make the Polish system work. Their attitude, he said, is "put any facade you want on it to placate the Soviets," but to show the people that officials committed to Poland's interests are actually running the economy, and the people will produce.

In other words, Derwinski said, do what "Deng Xiaoping has done in China -- operate pragmatically, with lip service to the Maoists."

It is Derwinski's contention that if the United States will provide the necessary "chicken feed" to carry Poland over the period of its worst food shortages and that if the "technocrats" he has talked to are correct and Poland can begin to operate an economy in which its people have confidence, the nation will be able to struggle back to its feet by its own means.

There is widely expressed suspicion in the Soviet Union and across Eastern Europe that the Reagan administration's ulterior motive in Poland is to prove Reagan's thesis that communism is collapsing. American policymakers insist that allegations that the United States wants chaos in Poland are unwarranted. On the contrary, they argue, a collapse of all authority in Poland would assure Soviet intervention. While that would confirm a failure of communism, it also could produce a situation of explosive unpredictability in the heart of Europe.

But some American officials acknowledge that there has been a clear difference in approach between the United States and its Western European allies over how to deal with Poland's large foreign debt and pleas for new loans.

The Western Europeans, with their greater stake in East-West detente, have been more willing than the United States to grant new credits to the founding Polish economy. The United States, as characterized by one senior official, has been more prepared to be liberal about rescheduling payment of Poland's debts, but less generous about providing new money.

Both approaches have been "self-serving" so some degree, the official conceded privately, in what has been "a running discussion with out allies." Western Europe is more ready to grant Poland new loans because more of the money is likely to be spent in Western Europe. The United States, in turn, has been prepared to take more criticism for lack of generosity, because it "wants to keep the pressure on" the Poles to reform, and also because it wants the Soviet Union and other Communist nations to pay their share for extracting Poland from economic "disaster."

The Carter administration turned down Poland's request last year for about $3 billion worth of loans and provided instead the $670 million in credits to purchase grain.

The United States then, and in the early months of the Reagan administration, was focused lopsidedly on the threat of Soviet invasion, many officials now concede. Too little attention was given, as one source put it, "to what the Soviet Union would do with Poland if it did invade -- and the enormous costs and consequences of military action."

Many Eastern European diplomats have insisted all along that the likelihood of Soviet military intervention in Poland was remote, because the Soviet Union recognized far better than the United States did that the costs of Soviet "action" were much higher than the costs of Soviet "inaction."

In effect, East and West have each other by the throat in Poland's economic crisis, in a web of relationships never dreamed of by Karl Marx, the father of communism.

While western capitalism has a heavy stake in Poland's economic survival because of its debts to the West, the Communist nations of Eastern Europe, as a consequence of East-West detente, have an even greater stake in the continuance of western trade, credits, and the supply of western technology.

Polish leaders have said that the Soviet Union supplied $4 billion in economic assistance during the past year. According to official American sources, Poland owes the West $26 billion in loans and credits.

Poland's real debt to its Communist allies is unknown and difficult to calculate because trade between Communist nations is largely on barter terms. But in the debt rescheduling agreement between Poland and its western government creditors in Paris last April, it was calculated that Poland was "in the hole" for $11 billion this year, U.S. sources said. Even if all the government-to-government debt rescheduling negotiations are completed as planned, the negotiations between Poland and some 460 banks in th West are all resolved and Poland's economy performs as its planners projected in April, these sources said, Poland will still have hugh debt payments -- $9 billion by American calculations -- requiring new rescheduling in 1982.

The American share of the Polish debt is relatively small compared to the Western European share. According to authoritative U.S. sources the U.S. government share of Poland's $26 billion indebtedness to the West is $1.8 billion and the American banks' share is $1.5 billion.

"It takes a heroic set of assumptions," said one senior Reagan administration official, to believe that Poland can pull off its effort to escape economic disaster. The international assumption always has been that the Soviet Union provides "umbrella" coverage for its Communist allies, and will never permit a nation in the Eastern European bloc to go into outright default because of the consequences for the entire bloc. But that is no absolute guarantee on which bankers are now so willing to bet.

The standard international safety net for nations in a state of structural economic crisis is to gain the financial resources of a multinational consortium, and to accept an economic stabilization program run by the International Monetary Fund. Some Communist nations, including Yugoslavia and Romania, are members of the IMF, and draw credits from it. But a basic stabilization process means "going through the economic wringer," as some characterize it, including "full disclosure" of a nation's books and accepting IMF staff members to scrutinize the process in the debtor nation.

Some U.S. officials believe it will come to that for Poland; others are convinced that the Soviet Union will never permit that degree of outside penetration of the Soviet bloc system. Still others say there is no certainty in either direction, because as one official acknowledged, "the Soviet Union already has swallowed more in Poland than any of us thought was possible."