IT WAS, as John Dean recalled it, the first major caucus of the Watergate cover-up. At 9 a.m. on June 20, 1972 -- barely 79 hours after the break-in at the Democratic National Committee -- there they all were, the men who were soon to play leading roles in the great national melodrama.

There was John Mitchell, chief of the Committee to Re-elect the President, puffing gloomily on his pipe; Presidential Assistant John Ehrlichman, scowling under his beetle eyebrows; White House Chief of Staff Bob Haldeman, his face deeply tanned from the weekend at Key Biscayne; fresh-faced, deferential John Dean, counsel to the president; and the new attorney general of the United States, ichard G. Kleindienst.

As Dean remembers it, this august assemblage in Ehrlichman's office seemed primarily concerned with the public relations aspects of the Watergate incident. Dean recalls that Ehrlichman asked who was "leaking" to the press. Kleindienst said it was the Metropolitan Police, but the leaks would be plugged as soon as th FBI took over the case. After the meeting, Dean says he hitched a ride with Kleindienst to the Justice Department.

Now, 13 years later, Kleindienst tells us he was never at this meeting. Moreover, he says, John Mitchell has told him he wasn't there either, indeed that he was never at any White House conference with Ehrlichman, Haldeman and Dean together. Thus, Kleindienst suggests the June 20 conference was largely John Dean's fabrication.

Why has the former attorney general waited all this time to raise this point of personal privilege? He says that because of the "sorrow" always evoked by memories of that time he long declined to read any of the Watergate memoirs. So not until he glanced through Dean's Blind Ambition while preparing his own book did he stumble across the account of the June 20 meeting.

But there is something curious about this story. It scarcely seems possible that Kleindienst could have missed accounts of the June 20 meeting which had been part of the conventional wisdom about Watergate a full three years before Dean's book appeared in 1976 and amply discussed in the press and Congress. It was of more than passing interest because from that meeting, first Ehrlichman and then Haldeman had gone into the president's office for tete-a-tetes with Nixon, apparently to brief him on the earlier meeting. Haldeman's notes of his talk with the president reveal the same concern with public relations. Yet, we know little about this Haldeman-Nixon meeting because it was the conversation interrupted by the infamous "181/2-minute gap," the result of an erasure -- intentional or accidental -- while the tape was in the custody of Nixon's personal secretary, Rosemary Woods.

All this is not to suggest that Kleindienst is consciously lying about his presence at the meeting. Indeed, there is something so earnest, so heartfelt about this book that it is difficult not to believe in the attorney general's sincerity.

BUT THERE is another explanation for his tardiness. As he puts it himself, "I knew I would be powerless, anyway, in that period of Jacobin fever, to correct any inaccuracies . . ." Clearly, in the midst of a conservative backlash, he feels the climate has changed sufficiently to clear his name, which he feels was besmirched by inaccurate press accounts, self- serving memoirs, vindictive prosecutors, and -- worst of all -- by his conviction for failing to respond fully to questions at a congressional hearing, which brought him a suspended sentence of one month in jail and a $100 fine.

Kleindienst reviews thets which led to that conviction -- the so-called "I.T.T. affair" in which the White House apparently intervened to water down the antitrust action against International Telephone and Telegraph. Although Nixon himself called Kleindienst on August 19, 1971, to order him to halt the ITT prosecution, Kleindienst told the Senate Judiciary Committee, "I was not interfered with by anybody at the White House. I was not importuned. I was not pressured. I was not directed."

In defense of his position, Kleindienst argues that he refused to follow the president's order and that the subsequent settlement of the ITT suit stemmed from quite different events. Yet, in light of that April 19 call, it is hard to see how he could tell the committee he was not "pressured" by anyone at the White House.

Elsewhere, Kleindienst vigorously defends Nixon's attempt to put Clement Haynsworth on the Supreme Court, argues that Archibald Cox was too partisan to serve as Watergate special prosecutor, and settles some old scores with John Ehrlichman.

Old scores, indeed. For whatever reason Kleindienst may have had for delaying this rebuttal, few readers are likely to care very much about the minutiae of events which most of the nation digested a decade ago.

And that is too bad. For there is a rough- hewn kind of honor about the man which sets him apart from the sleazy gang which staffed the Nixon White House. He probably deserves somewhat better than he's received at the hands of history -- but, at this remove, it will be hard to set the record straight.