President Reagan said yesterday that "some anti-religionists are trying to break down" the "wall of separation" between church and state in the Constitution, and asserted that his remarks on the subject have not been properly quoted.

The president did not identify the "anti-religionists" as he paused briefly to speak to reporters before leaving for Camp David, Md.

Reagan was asked about Walter F. Mondale's speech Thursday accusing the president of tampering with the wall between church and state and the Democratic presidential nominee's remark that "most Americans would be surprised to learn that God is a Republican."

At that point, an ABC News tape recording indicated, White House spokesman Larry Speakes advised Reagan: "Best don't answer that."

"I have no answer to any of those things that what's-his-name said," Reagan remarked.

The president was then asked if he still believes, as he said during the Republican National Convention, that politics and religion are "necessarily related."

That comment, and a recent letter to ministers from Sen. Paul Laxalt (R-Nev.) urging them to register voters in support of Reagan, has stirred criticism from Mondale and others. Reagan advisers have said they want to move on to other campaign issues.

In recent days the president has stressed his belief in the separation of church and state, and yesterday he said he stands by his remark "in the sense that I said it in Dallas, which none of you have correctly reported."

"The correct version is there is a wall of separation, some anti-religionists are trying to break down that wall, and what I was saying was in the context of yes, definitely there is a connection between morality and politics and should be and too many neglect it."