President Reagan, in an interview broadcast today, defended what he called the "reformist administration" of South African President Pieter W. Botha and contended that it has eliminated segregation in public places.

"They have eliminated the segregation that we once had in our own country -- the type of thing where hotels and restaurants and places of entertainment and so forth were segregated -- that has all been eliminated," Reagan said in a telephone interview taped Saturday with WSB Radio of Atlanta. "They recognize now interracial marriages and all . . . . For us to take an action now such as some are suggesting, turning our backs and walking away would leave us with no persuasive power whatsoever."

White House spokesman Larry Speakes acknowledged later that "some" rather than "all" public segregation has been eliminated and said the president was aware of this.

Most of the changes cited by Reagan in modifying "petty apartheid" have occurred on a limited scale. However, his assertion that segregation "has all been eliminated" in public places is inaccurate, as Speakes acknowledged.

Only specially designated international hotels now admit persons of all races, as do some restaurants and some places of entertainment. But a number of these facilities, particularly in smaller communities, remain segregated.

Reagan made no comments about such major features of apartheid as segregated education or the fact that blacks are denied voting rights. He repeated the Botha government's contention that the black majority in South Africa is "a combination of minorities" because of tribal divisions.

In another telephone interview, with Washington Broadcast News, Reagan once more criticized pending congressional attempts to impose economic sanctions on South Africa.

"I will tell you that I am basically opposed to the idea of punitive sanctions," Reagan said. "I think in this particular case, South Africa, they would hurt the very people we are trying to help."

Reagan declined to say whether he would veto a sanctions measure if it reaches his desk, "because you never know just exactly what it's going to look like when it gets there." But senior administration officials said last week that Reagan has resolved to veto any sanctions bill, although he may take milder action against South Africa by executive action.

Reagan's latest comments in defense of the South African regime and his policy of "constructive engagement" to work quietly for moderation of apartheid were the highlights of three seven-minute telphone interviews he gave on Saturday.

In an interview with WRHC of Miami, the president was not asked about South Africa but did defend another kind of sanctions, "the restraints and restrictions that we have with regard to our relations with Cuba."

Reagan said the United States would be "very happy to help open the door" for Cuba if it wanted to prove by deeds instead of words that it was ready "to come back to the community of American nations."

"But at the present time, they are openly a satellite of the Soviet Union and taking their orders from the Soviet Union," Reagan said. "And we see no opening for us to be of help."

Asked whether Central America and the Caribbean will be "entirely" free of communism when he leaves office, the president said there has been progress but added, "I don't know whether we can accomplish that 'entirely' -- to qualify that word." Reagan said the progress "is far more outstanding than many of us have realized over the last couple of years."

In his interview with WSB, Reagan said his administration has made it plain to South Africa that "apartheid is very repugnant to us." He then defended U.S. policy, which he said has been responsible for "some very substantial changes" in the country.

He said these changes include allowing blacks to join labor unions and have their own unions, buy property in formerly white areas and own businesses "in some 40 white-dominated business districts."

The president said he was "very pleased" to see the "clarifying statement" of the Rev. Jerry Falwell, head of the Moral Majority, in which he apologized for calling Nobel prize winner Bishop Desmond Tutu "a phony."

Reagan said Falwell had "mistakenly used the word to describe the thing that he had found, that he was not recognized as a 'black leader of all the blacks.' "

The president was asked whether he fears a pro-communist government might take power in South Africa if the Botha government collapses. He replied indirectly, saying that he thinks that the Soviet Union is, "in its usual style, stirring up the pot . . . . "

In the Washington Broadcast News interview, the president said he was looking forward to his November summit meeting with Soviet leader Mikhail Gorbachev in order to set "an agenda for the future so that we can eliminate the hostilities and the suspicions, if that's possible." He then denounced the Soviet Union.

"There's no question but that the Soviet Union has made it plain that they are embarked on an expansionist program," Reagan said. "They believe in the one-world communist state -- the world revolution."