Former secretary of state Henry A. Kissinger has attacked President Carter's policy on Zimbabwe-Rhodesia as one that favors "the radicals against the moderates" and that could led to increased Soviet and Cuban intervention in southern Africa.

Kissinger's criticism - in many respects the harshest he has leveled against the Carter administration's foregn policy - is contained in an interview with The Washington Post editorial page staff. The full interview is contained on the opposite editorial page of today's editions.

The main thrust of his criticism was directed at Carter's finding last month that the recent elections leading to a black majority government in Zimbabwe-Rhodesia under Prime Minister Abel Muzorewa were not sufficiently free and fair to justify ending U.S. enconomic sanctions.

Justifying the maintenance of sanctions by questioning the Zimbabwe-Rhodesia constitution, Kissinger asserted, has had the practical effect of putting the United States on the side of "ideological radical" guerrillas who refused to participate in the elections and who have continued to seek power in the southern Africa country through armed struggle.

Kissinger said that when he was secretary of state he had sought "to co-opt the program of moderate evolutionary reform, that is to say majority rule and minority rights"

By that, he explained, his aim was to isolate those ideological radicals with "a program of majority rule so extreme as to be incompatible with the survival of the (white) minority and, therefore, incompatible with the peaceful evolution of the larger problem of South Africa."

But, Kissinger charged, the Carter administration - largely because of the influence of United Nations Ambassador Andrew Young - has attempted to win favor with back Africa and the Third World by pursuing policies aimed at ensuring the guerrillas a role in the government of Zimbabwe-Rhodesia.

"Should we be on the side of those who are willing to rely on evolution, or on the side that seeks its aim by guerrilla warfare?" he asked ". . . if the side that threatens to continue fighting can set the terms, them we are encouraging the continuation of the fighting and an escalation of radical demands. The inevitable result will be that the most radical elements will dominate."

"We run the risk of a verbal position that is radical, a practical position that is impotent and a theory justifying Cuban and Soviet intervention whenever they judge it is time to heat up conditions again, "Kissinger warned.

"I fear that we have been practicing in favor of the radicals against the moderates," he said. "That course will lead to war between the races. But it is not too late to change; we still have some margin for maneuver and some time. This is why I am speaking out."

Kissinger also was highly critical of the administration's policies toward Nicaragua, where it is engaged simultaneuosly in trying to force the ouster of President Anastasio Somoza and bring about a succession by moderate political elements rather than the radical Sandinista guerrillas fighting Somza.

Referring to the administration's human rights pressures on Somoza, Kissinger said: "My impression is we did enough to unsettle the existing government but not enough to put over a moderate alternative, if there is one . . . I could have understood a decisive move to replace Somoza with a moderate element. But this would have required the kind of covert action so much decried today."

"If the sole alternative to Somoza is the Sandinistas, we may reap the whirlwind," he warned. "If the radical left becomes dominant in Central America, even Mexico will feel the pressure."

After discussing such other countries in turbulence as Iran and South Africa, Kissinger concluded with a warning that the United States should not - in the name of human rights and respect for democracy -identify automatically with any radical movement that arises in opposition to dictatorial regimes.

"Any proposition can be manipulated for undesirable ends," he said. "I trust we are wise and strong enough to know the distinction. I am asking us to define a position which reflects our values, but our values do not require the encouragement of radicalism.And we must be aware of the international angers lest we create chaos without having an alternative." CAPTION: Picture, HENRY A. KISSINGER . . . "not too late to change"