H. R. Haldeman, whose published version of major events during the Nixon White House years has triggered nationwide reaction, credits Richard M. Nixon with acts of statesmanship that twice saved the world from nuclear confrontations.

One of them, he contends, "was the most dangerous of all the confrontations this nation has ever faced."

That incident, according to Nixon's top White House aide, came in 1969 when Russia moved nuclear armed divisions within two miles of the Chinese border and threatened to attack China's infant atomic plants, after "several" Soviet overtunes to the United States to join in a surprise "surgical" strike.

A last minute stratagem devised by Nixon and foreign affairs adviser Henry A. Kissinger caused the Russians to pull back their warheads, Haldeman writes. What the Americans did was suggest that they might try to discuss the tense situation directly with China. Russia, fearful that the United States and China might join against it, then drew back its forces.

The second nuclear incident Haldeman described was in Nixon's second year, when the Russians allegedly provoked a second type of Cuban missile crisis.

Haldeman wroter that Maj. Gen George Keegan, then head of Air Force intelligence and now retired, used an additional stratagem in this crisis that had worked in the original Cuban missile confrontation: inform the Russians that they had too much to lose to make a nuclear war thinkable.

In 1962, according to Haldeman, Keegan had sent a message - deliberately uncoded so the Soviets could intercept it - to the U.S. Defense Secretary informing him that the United States "had 1,000 nuclear weapons air borne and named Soviet cities which were targeted for the bombs."

In 1969, Haldeman wrote, Keegan sent a similar message for Soviet ears stating that a nuclear attack on China would kill thousands of Siberians with fallout.

Keegan said last night that the Haldeman account was basically correct but added that the 1969 warning was information passed to the Soviets verbally rather than by way of a military communication designed to be intercepted.

These accounts, along with much else of Haldeman's memoirs made public yesterday in advance of serialization and book publication, drew instant rejoinders - and rebuttals.

Haldeman's book, "The Ends of Power," had been sold to about 30 U.S. papers and some 20 others overseas for more than $1 million, publishing industry sources estimated yesterday. A West German magazine reportedly paid $250,000 for the rights. The New York Times syndication service had timed release of the material for next Monday, one week before the book's publication date.

But a report of the revelations in the book in yesterday's Washington Post caused many of the papers that had bought serial rights to rush their material into print. The result was a spate of articles and television specials of various versions of Haldeman's descriptions of the Nixon Watergate years, and an outpouring of comment - much of it critical.

Leading the list was a one-sentence statement issued by Nixon's office in San Clemente, Calif:

"Former President Nixon's memoirs will be published in May."

That was all the former president had to say about charges by his once closest aide that he had "caused" the burglars to break into the Watergate and later had tried to erase incriminating taperecordings.

Other major figures from the Nixon administration denied most of Haldeman's more sensational asserations.

Appearing on NBC's "Today" show, former Secretary of State Kissinger was asked about Haldeman's report that Russia had asked the United States to join in a preemptive nuclear attack on China.

That is not true," Kissinger replied. "All the papers on foreign policy matters run across my desk and I do not recall any such event and I would not have forgotten it."

Kissinger was less certain about Haldeman's statement that the Russians had massed hundreds of nuclear weapons on the Chinese border.

"Again we were concerned about the possibility of a Soviet attack on China, but that did not arise from any particular Russian warning to us," he said. "Again, this seems to be a very large number. I do not think this could have dodged us."

Pentagon sources said that in discussing military events of the Nixon presidency, Haldeman had taken a "worst case" view of the Soviet nuclear submarine activities in Cuba.

Haldeman wrote that Soviet strategy called for using Cuba as a base for ships carrying the Russian Styx cruise missile. The Styx, he said might be employed to "knock out" American command centers, causing enough confusion to "delay the American retaliation to greatly reduce its effectiveness."

Such a situation, he said, "might even catch a good portion of our nuclear force on the ground," perhaps making a surprise attack on the United States "an acceptable proposition" for the Soviet.

Military specialists said last night the Haldeman published account does not square with the military concerns that were expressed by Nixon administration officials at the time in 1970.

It was not the Styx cruise missile they were worried about, but submarine missiles. The Styx cruise was a shipboard weapon not even capable of reaching U.S. inland command centers, while the nuclear powered Echo class submarines carried missiles ranging up to 400 miles.

The Post, on Wednesday, did not have those portions of the Haldeman material that deal with these two nuclear incidents.

But most of the reaction yesterday to Haldeman's book dealt, as does his manuscript, with Watergate.

One new element emerged among the welter of stories yesterday - Haldeman's brief remarks about what might have been contained on the celebrated 18 1/2 minute "gap" on a crucial Nixon tape.

Halderman testified at the Watergate cover up trial that he could not remember what had been said on that missing conversation three days after the Watergate break in. As Newsweek Magazine notes, in its account of the Haldeman book, "he might thus be liable to a new perjury charge if his memory suddenly unclouded in his book."

In his book Haldeman reconstructs what he and Nixon "might thve" said that day. This "guess" puts more of the blame for Watergate on Nixon and his White House aide Charles W. Colson.

Haldeman voices a "theory" that Nixon might have said: "I can't stand an FBI interrogation of Colson . . . Colson can talk about the president if he cracks."

In the earlier accounts of his book, Haldeman dealt harshly with Colson. Yesterday, Colson replied.

He denied Haldeman suggestion that Nixon had instructed him to "get the goods" on Democratic Chairman Lawrence O'Brien, thus leaving to the Watergate break in.

"False," he said. "It just didn't happen that way."

He and Nixon had discussed O'Brien often, he said, and attempts were made to investigate O'Brien's fundraising techniques. But that occured months before the June 17, 1972, breakin, he insisted.

In a separate telephone interview with The Post, Colson confirmed one incident Haldeman reported - that Haldeman "had dressed down" Colson so severly as to leave him sobbing.

But he said the circumstances of that meeting were totally different from what Haldeman described. What triggered the incident, he said, was an emotional confrontation with Haldeman after learning that he had secretly tape-recorded a dinner meeting of high government officials.

The taping, according to Colson, took place in Blair House in 1971 shortly after than Treasury Secretary John B. Connally had switched parties and joined the Nixon administration. Connally spoke there that night. Colson said Haldeman never explained why he taped the meeting.

"I told him I was tired of his tactics." he said. "I told him I was leaving the White House."

Colson said he and Haldeman later became reconciled, but that incident "should have tipped me off" to his method of operation.

"If I had left, I might not have gone to prison," he added.

At the same time, Colson expressed "great compassion" for Haldeman. "I don't believe in name calling," he said, " . . . it's really rather unseemly for any of us who were involved to be pointing fingers at one another."

There was almost as much reaction to the circumstances of publishing Haldeman's story as to what he actually said.

Yesterday brought a flurry of activity in publishing circles, along with recriminations about The Post's article that upset all the schedules carefully arranged for syndication.

The contents of the book had been protected with extraordinary security. "Everybody thinks this was all hype for us." said Thomas Lipscom president of Times Books, Haldeman's publisher. "but it wasn't. It was extremely costly as well as being a tremendous pain in the neck."

Leonard Schwartz, vice president for marketing at Times Books, said the firm set the manuscript on three Linotype machines kept under constant watch by security guards. When the printing plant wasn't working, the 4,000 pounds of lead were locked in the Park Avenue offices of Times Books, and when the work was finished the lead was melted down.

But yesterday all the became moot. At 11.30 a.m The New York Times made the decision to run all of its excerpted masterial in Friday's editions. And it informed publications that had bought it that they were free to publish when they wished.