Zimbabwean Finance Minister Enos Nkala accused the Reagan administration today of trying "to dictate" internal economic and political policies of Third World countries by imposing tougher conditions on financial assistance from the International Monetary Fund and the World Bank.

The sharp criticism by Nkala, who returned from the IMF-World Bank conference in Washington two days ago, marked the first public criticism of Reagan administration economic policy by this key southern African country.

"By laying overemphasis on the private sector the American government is trying to transpose its own policies onto other people," the minister said in an interview. "My view is that it's going to rebound on the Americans because an anti-American attitude is beginning to emerge" in developing countries.

The Americans, he said, "are too arrogant. They want to dictate what people should do."

"Until now the United States has gotten lots of mileage from its pledge" earlier this year of $225 million in aid to Zimbabwe over three years, a Western diplomat said.

The West, led by the United States, held out at the Washington meetings for maintaining current IMF conditions in granting loans to assist in short-term balance-of-payments problems. The Reagan administration also stressed private rather than public lending and raised questions about proposed new multi-billion-dollar commitments to the World Bank's International Development Agency, which provides interest-free loans to the world's poorest countries.

Poor countries have long chafed over IMF conditions for assistance, often including devaluation, tighter money and controls on public spending and imports.

Nkala, who spent 10 years in prison with Mugabe during the guerrilla struggle for black-majority rule, has long been noted for his political outbursts. In some cases Mugabe has distanced himself from Nkala's remarks but in the economic field, Nkala has spoken with authority.

"America is now moving toward a direct confrontation with Third World countries," he said. "There was sharp concern by developing countries over the role the Reagan administration is playing" in the World Bank and IMF. The role, he said, could have "detrimental consequences for developing countries."

"In many areas, the ugly American hand is being seen as threatening to destroy the viability of the Third World economies and their political institutions and people are now beginning to take defensive actions," he added.

"There has been some foolish thinking in the American administration that they are everything to everybody," he said. "There are many alternatives. One alternative is to say, 'Out with the Americans,' and to look for other friends elsewhere. The world does not consist of the Americans. America is not the only wealthy country in the world."

He cited oil-rich Middle East nations, France and the Scandinavian countries as possible other avenues of assistance and added: "It's easier for many countries to say to hell with the Reagan administration."

A Western diplomat noted that the countries Nkala mentioned are not in the business of extending balance-of-payments support at favorable interest rates like the IMF.

"They don't have to take the money from the IMF," the diplomat added, noting that the IMF is not an aid institution but rather a means to obtain short-term assistance to alleviate balance-of-payments problems.

Zimbabwe received its first assistance from the IMF last year when it got 37.5 million SDRs -- special drawing rights, the IMF "currency" -- which is now worth about $43 million.

Zimbabwe's reserves have dropped in the last year from $210 million to $150 million as the newly independent nation has embarked on an expansionary program after 15 years of economic isolation because of international sanctions against the illegal white government.

Nkala said he had talks in Washington about further balance-of-payments support, noting that the discussions centered around the high level of food subsidies and increasing government spending, which is scheduled to rise by 37 percent in the current fiscal year. The $225 million in food subsidies make up about 8 percent of the $2.8 billion budget.

The diplomat noted, however, despite Nkala's complaints about the IMF, that Zimbabwe has already met some of the fund's conditions by raising interest rates and cutting back imports. "I can't help but think the moves are linked" to the appeal to the IMF, he said.

Nkala was careful to say there was no problem over bilateral U.S. aid, amounting to $75 million a year. State Department officials told him there was "no relationship between the aid pledged and the new American policies," he said. "I don't think the Reagan administration would be that foolish to stop the aid because we reject some of their policies."

He also accused the United States of indirectly inciting South Africa to "squeeze" the Zimbabwe economy through the Reagan administration's "accommodationist policy" toward Pretoria.

"It shouldn't be forgotten that America has investments here. Whatever screws are being pushed against us will necessarily affect" American companies here, he said.

It is estimated that American investment amounts to less than 20 percent of the $2.5 billion foreign capital in the country while South Africa accounts for almost $850 million.

Nkala accused Pretoria of trying to pressure Zimbabwe's economy by causing transportaton difficulties, ending a preferential trade agreement and expelling Zimbabwean workers.

South Africa should realize "before recklessly embarking on some program" that nearly a third of Zimbabwe's whites are South African, he said. It should "also know that there are massive investments in this country which should generate income for their investors and any actions which undermines" the economy necessarily undermines "the dividends of their own people."