Marc Rich, the reclusive American commodities trader who has taken refuge in Switzerland while resisting a U.S. investigation of his firm's international operations, contends the documents sought by federal prosecutors would unmask the company's role as middleman between countries that cannot openly do business with one another.

This account of Rich's motives appeared yesterday in several Swiss newspapers, based on interviews with Rich and some of his associates. These are the only interviews Rich has permitted since he abruptly abandoned New York this summer and moved to Zug, Switzerland, a small farming community and tax haven near Zurich. Zug is the headquarters of his company, Marc Rich & Co. A.G., considered to be the second-largest commodities trading company in the world.

Federal prosecutors in New York have been investigating whether Rich & Co. evaded taxes on $20 million in income by shifting profits from its American subsidiary to the parent company in Switzerland, where the tax burden is far lighter.

The documents sought by U.S. authorities would reveal Marc Rich's role as go-between in crude-oil shipments from Soviet bloc nations to South Africa--nations that are not on formal speaking terms, according to Swiss accounts. The documents would also itemize shipments of Iranian oil to the United States through Marc Rich & Co. during the peak of the Iranian crisis and the embargo imposed by the Carter administration, according to the accounts.

The interviews shed no light on the future disposition of the company's Swiss files--the target of a tug of war between U.S. and Swiss authorities.

After the documents were subpoenaed earlier this year, Rich resisted to the point where U.S. District Judge Leonard Sand finally imposed a $50,000-a-day fine on Marc Rich & Co. for contempt of court.

Last month, Rich seemed to give up, paying $2.6 million in fines and putting up securities worth $55 million as collateral to cover any future fines, while promising to supply the documents sought by the government.

But the apparent cease-fire erupted on Aug. 9, when federal agents, acting on a tip, seized two steamer trunks of records from a Swissair jetliner just before it took off on a flight from New York to Geneva and Zurich.

Swiss federal police then impounded the Marc Rich files in Switzerland that the company had promised to surrender, contending that their delivery to the United States would violate Swiss regulations against revealing "business secrets" to a foreign government.

Judge Sand has scheduled a hearing for next Monday on the status of the American-Swiss dispute and the role of Marc Rich in the battle over the documents.

In interviews with Swiss journalists this week, Marc Rich and his associates indicated that disclosure would be devastating to their business. Even the fines imposed by Judge Sand are less of a threat than the loss of the firm's credibility, they said. If Marc Rich's clients feel there is a risk that business documents will end up in the United States, they would break off business with the trading company, Marc Rich's associates reportedly contended. Accounts of the interviews appeared in the Zurich Tages Anzieger and the Schweizerische Handels-Zeitung.

They said that the legal action in the United States and the publicity surrounding it has largely destroyed the business of its U.S. subsidiary, which accounted for about one-fifth of the firm's worldwide revenues. The firm was sold June 30 to several of Marc Rich's associates who are not American citizens.

The mantle of secrecy that covers the case suits its central figure. Rich, 48, escaped Belgium at the age of 11, fleeing Nazi persecution of Jews. He attended New York University, and went to work for one of the world's leading commodity firms, Philipp Brothers in New York.

Rich became a legend in the trading business in 1973, when he used his Middle Eastern contacts to obtain crude oil supplies from Iran and Iraq for U.S. oil companies in the midst of the Arab oil embargo. The transactions earned millions for Philipp, but when Rich and the firm quarrelled over the size of the bonus he had earned, he left to form his own company, joined by a friend and colleague, Pincus (Pinky) Green.

The Swiss journalists describe Rich as a discreet, sensitive, somewhat shy man who also seems poised for instant action--reflecting the bold trading style his company has exhibited.

The exact wealth of Marc Rich & Co. today is not known, since the company does not publish financial results, but according to industry estimates, the company last year traded more than $10 billion in crude oil, aluminum, tin, lead, zinc, copper and bauxite. In 1980, it declared on Swiss tax forms revenues of $10 billion and a profit of almost $200 million, according to Swiss accounts. With other investors, Rich owns a controlling interest in 20th Century-Fox.

Rich and his associates broke their silence this week to give their side of the case to Swiss journalists, saying that the abortive shipment of documents on the Swissair flight was not an attempt to evade U.S. subpoenas--the documents were to have been reviewed by the firm's lawyers in Switzerland, then returned to the United States.

Their effort to maintain secrecy was motivated by the need to protect the privacy of their transactions, they told Swiss journalists, not to frustrate U.S. law enforcement officials. But they are reconciled that continuing prosecution of the firm in the United States is now inevitable.