In the past few days Prime Minister Maurice Bishop of the tiny Caribbean island of Grenada has been in Washington trying to see President Reagan to assure him that Reagan was wrong when he said recently that Grenada was building an airport for Cuban and Soviet military use.

The airport will be for commercial use, and not for any Soviet or Cuban military venture, Bishop says. But the White House won't see Bishop, who is here on a private visit at the invitation of TransAfrica, a black lobbying organization.

For several years, Grenada has made diplomatic overtures to the United States that have been met with snubs and stony silence.

While the American government privately explains that its coldness is due to Grenada's close ties to Cuba, what is the harm in dialogue with Grenada? We sell grain to the Russians, court the Chinese, even "constructively engage" the South Africans, who are ostracized by nearly every other country in the world.

So the refusal to talk to this small island nation not only pushes Grenada further toward the left but makes the United States look mean-spirited.

On Saturday night, at a dinner of black Americans interested in foreign policy, Randall Robinson, head of TransAfrica, drew laughter and applause when he put the problem this way: "Grenada is a nation one-fifth the size of a congressional district, 10 by 20 miles, but this mammoth nation to the north has determined it to be a threat to its interests and security." He might have added that its biggest export is nutmeg.

It is equally wrong to punish Grenada by using U.S. influence to try to persuade international financial institutions to withhold aid, a policy begun under Jimmy Carter and intensified under Reagan.

A recent study ordered by Congress, undertaken by the Congressional Research Service and obtained by the Wall Street Journal, quoted an administration source as saying that former secretary of state Alexander M. Haig ordered that Grenada not get a penny of indirect aid from the International Monetary Fund.

Moreover the study, by Caleb Rossiter, an assistant professor in Cornell University's Washington program, says the United States has what some administration officials informally refer to as a hit list of countries and that it tries to prevent those nations from borrowing money. On the list, the study says, are Vietnam, Cuba, Afghanistan, Nicaragua and Grenada.

Yet the United States actively supported a $1.1 billion loan to segregationist South Africa last November on the grounds that opposing the application would have politicized the IMF. The administration also has fought a new anti-apartheid amendment to IMF participation, saying apartheid is a political issue and would violate the IMF's economic sanctity.

In 1979, within weeks after Bishop's leftist forces overthrew an unpopular government, Bishop said Cuba sent diplomats, aid and arms in response to his call for help, which he said was directed to the world at large.

The United States expressed its "displeasure" over close Cuba-Grenada ties, and its regret that the U.S. budget didn't contain monies for bilateral assistance to Grenada, according to newspaper accounts at the time.

Thus, even Grenadians who were unhappy about Cuban influence decided that the United States was acting like a rather stingy bully.

Bishop responds to questions about his intentions to turn Grenada into a Marxist society by acknowledging that his government regards itself as "revolutionary," sympathetic to grass-roots revolutionary movements and "nonaligned."

I have problems with the fact that Grenada holds political prisoners without trial, that the country has not in four years held elections and that there is no freedom of the press.

Bishop has announced steps he said will lead to elections. We will wait and see. But these are the legitimate concerns that the United States should address, rather than using international financial institutions as weapons and rather than refusing to talk with visiting prime ministers.