The deposed shah of Iran regrets having followed "a policy of surrender" to his opponents during his final days in power and says he now wishes he had used military force to put down the demonstrations that broke his rule.

His own miscalculations coupled with conflicting signals from the American and British governments produced this failure, according to the shah. The White House set him private signals that it would back up a strong military repression of the demonstrations that eventually toppled him, but each time he sought official confirmation from Washington, "the American ambassador told me he had no instruction on that," the shah recalls.

"Now many people say that if my government had enforced law and order there would have been a hundred times less casualties than there have been in the last 15 months. We don't know how many people have been massacred. And it continues every day, every day and every night," the shah, Mohammad Reza Pahlavi, said in the most extensive interview he has given since fleeing Iran on Jan. 16, 1979.

The shah spoke for two hours on Friday as twilight was falling across the spacious enclosed gardens of Cairo's Kubbeh Palace, the official residence here for visiting heads of state. The palace is the current, and perhaps final, home in exile of Pahlavi, who has been living in near isolation here since an operation was performed on him March 28 to remove his spleen.

He said he had gained 10 pounds in the last 10 days as the effects of chemotherapy have begun to fade. He showed the signs of a beginning suntan. But there were also signs of his continuing battle against cancer. The elegantly tailored double-breasted suit he wore fit loosely about his once fuller shoulders and chest, and his horn-rimmed glasses loomed prominently on his birdlike, still emaciated features.

Another indication that undercut the appearance of temporary recover of color and some strength after two emergency operations on the 60-year-old former monarch came when Pahlavi paused frequently to breathe in deeply as he answered questions during the interview with Katharine Graham, chairman of the board of The Washington Post Co., and this correspondent.

The shah also sighed frequently as he spoke, particularly as he repeatedly contrasted Iran's material progress under him and his grandiose dreams for its future with what he described as the current destruction of the nation "by the arsonists and terrorists" now in power in Tehran.

Resentment, anger, nostalgia and a strong hint of loneliness all eddied through the conversation, which he lingered over and ended only when called away through the cavernous palace for a long-distance telephone call. Outside, his wife and his youngest of two daughters were riding a bicycle around the palace grounds.

Seated in a front-hall waiting room, the shah condemned the United States and Britain for failing him during the crisis, for shunning him since, and for seeking to deal with the Islamic revolutionary regime in Tehran.

Saying that he had decided to begin to speak out much more forcefully on past and present events in Iran, Pahlavi ruled out abdicating even though he indicated at several points that he has accepted the likelihood that he has lost power for good. Abdication, he asserted, would not help free the 53 American hostages being held in Iran by captors demanding the shah's return for trial.

As long as the United States and others in the West are ready to deal with terrorists and bloodthirsty savages, which are now pretending to represent my country, how can anything be achieved? I don't know how people are prepared to shake hands with these people," Pahlavi said. "First, when they started to destroy my country and just assassinate all these people, the West tried to almost excuse these people and give them some kind of respectability."

Moreover, the shah did not rule out lending himself to a drive by what he called "the patriotic people in Iran" should they move against the government ruled by Ayatollah Ruhollah Khomeini.

"If the patriotic people in Iran could not take over, it would taken over by the communists," the shah said. "It is a question of time now." His own role "depends on the people of Iran, what do they want," he said.

The shah made these other points:

He feels he bears no responsibility for the taking of the American hostages by Islamic extremists protesting the shah's admission to the United States last October for medical treatment. The Carter administration has told him that it was confident at the time that the embassy was adequately protected, he said.

He had considered asking the White House to live up to a promise to readmit him to the United States when he left Panama on March 23 after deciding he could not get safe medical treatment there. But he did not make the request. Asked why, he said: "Maybe the price would have not been worth it" for the Carter administration. He said he could not elaborate now.

He is convinced now that "the West wanted this Islami republic, perhaps thinking that with Islam it could contain communism." He specifically blamed the British and American governments and the Western media for promoting his downfall. "Well, now you have it. Are you happy? Do you have human rights there now? Democracy? Liberalization?" What they are doing to my country in the name of Islam just makes people go away from Islam."

He decided not to come directly to the United States in January 1979, as the Carter administration was urging him to do, but stayed in Egypt then "because all my friends were saying 'don't [leave].' Some said I should stay closer to my country, maybe for a return. And some people were saying how could I go to a place that did this to me."

Pahlavi's continued presence in the region, then added to the fears of the Islamic revolutionaries in Tehran that he would attempt to duplicate his 1953 return to power with the help of the Central Intelligence Agency after a brief exile. He went from Egypt to Morocco, to the Bahamas and then to residence in Mexico, before flying hurriedly to New York in October 1979 for an emergency gall bladder operation. The hostages were seized on Nov. 4. The shah left for Panama on Dec. 15.

The shah currently is at work revising a book on his downfall that was published earlier this year in French. The revision will include sharp questioning of the American role in the Iranian crisis, he indicated.

The shah seemed eager to chat with outsiders. He, his wife, and two daughters, aged 9 and 17, live in a rambling, ornately furnished palace of several hundred rooms that has been used as a guest house for presidents Nixon and Carter and other visiting heads of state in recent years. Egyptian President Anwar Sadat has also provided the shah with an Egyptian chamberlain, a household staff and heavily armed security forces who watch over Pahlavi and the family as they would a reigning monarch. Sadat seems to be a regular visitor.

The shah's tone was somber, and his voice frequently trailed off as he returned again to the horrors of summary executions, the kidnaping of American diplomats and the collapse of central authority that have replaced his dreams of putting subways in every city and spreading literacy, affluence, electricity and other benefits throughout a country that under him had come "to the threshold of joining the most developed and fortunate countries of the world."

As he did when he was in power, he brushed aside accusations that his government had ben marked by secret police torture of political opponents and corruption from which his family had profited. He said "liberal circles" in the United States had helped pave the way for the Soviet thrust into Afghanistan by opposing even greater arms shipments to Iran. "A militarily strong Iran would have established and kept peace in the region," the shah said.

His transition from authoritarian ruler with dreams of grandeur to a dispossessed Persian nobleman dependent on an Arab nation's hospitality is still incomplete.

He was most at ease slipping back into memories of the innovative call he made more than a decade ago for an international summit of selected countries to reach a global economic copact that would have covered energy and trade, and in outlining his geopolitical strategy for resisting the Soviets in the heartland of OPEC.

But he ruefully conceded in the next breath that the Western nations largely ignored the economic compact idea until recently, and that he sees Western strategy as having been fatally undermined by accepting "one fait accompli after another," including his ouster and the Soviet invasion of Afghanistan.

A simple change of phrases was most revealing of the twilight world the shah exists in so uneasily. "For the last year of my reign," he began and then paused. "I mean, for the last year that I was in my country . . ."

Asked about adjusting to his loss of power, the shah voiced a strong measure of fatalism. American officials claim this streak of fatalism was more important to his failure to throw his Army fully against Iran's massive protests in 1978 and 1979 than were American policies.

"I have always been a very mystical person, so I accept everything that happens as the will of God, or destiny, or whatever you want to call it," he said. "I take it as it comes, philosophically. This doesn't prevent me to think, and to sigh, and eventually to weep inside for what is happening to my country."

He did not resemble the photographs of the gaunt, skeleton-like figure who flew from Panama to Egypt two months ago for the removal of an enlarged, cancerous spleen. Observers said at the time that he appeared to be making a last stand against death. The Iranian militants holding the American hostages ridiculed such accounts, saying that he was well and that the trip was part of a plot to put the shah back on the throne.

"I was looking rather miserable a few days ago," Pahlavi said in his fluent English. "I was very ill." He said that the fading of the effects of chemotherapy had allowed him to gain weight, but added that he still suffered pain from his multiple illnesses. He said he would have to undergo chemotherapy every three weeks for another five months. He said he will stay in Egypt for the foreseeable future.

His account of receiving confusing American signals as he sought help for his collapsing regime would appear to provide confirmation of recently published accounts, based on U.S. sources, that suggest that President Carter's national security adviser, Zbigniew Brzezinski, sent private messages to the shah through Iranian Ambassador Ardeshir Zahedi urging harsher military reaction to the demonstration, while Secretary of State Cyrus Vance refused to give official American backing to such a course.

The shah's generals did order their troops to fire on demonstrators and killed hundreds of the protesters, calling for the shah's ouster during the months of turmoil that preceded Pahlavi's departure. But for reasons that are still in dispute, the troops either refused or were ordered not to confront Khomeini's supporters in the climactic demonstrations of January and February 1979.

The shahs bitterness toward the American role was evident throughout the conversation. Asked if he felt the Carter administration had let him down by not admitting him when he left Panama, he replied, "Yes. From the start, yes. It started a long time ago. It is nothing new."

Earlier, he said, "My biggest mistake was in listening to the Americans and to the British about our internal problems . . . Looking back, [the wrong advice] was freeing all the terrorists from jail and letting them loose, giving them the possibility of leading the band of arsonists and terrorists. And, always trying to water down or at least let the government, yield to the pressure of the looters and arsonists, that is, permitting the government to follow a policy of surrender to these bandits."

He said U.S. advice, relayed through ambassador William Sullivan, had helped persuade him to follow a policy of trying at the last moment "to find a solution of bringing in the opposition to power. That was even my own policy. Now I can see that was wrong. I decided not to spill blood." He said instead he should have ordered the military government he established in November to "establish law and order."

He said the Americans and British ambassadors in Tehran had abandoned him to back secular opposition politicians led by Mehdi Bazargan. The policy "paved the way for Khomeini. They saw we were surrendering under duress and pressure; and they decided they should go all the way."

Asked about reports of messages being sent to him from Washington suggesting that he use an "iron fist," the shah said:

"Each time I was asking the American ambassador for confirming such kinds of news, he was always saying he had no instructions."

Asked if the messages came from Brezezinski via Zahedi, the shah said: "Sure, sure. When I wanted to have a check and confirmation, always 'we have no instructons.' The official signal was blank. How do you want to operate this way in your foreign policy? Maybe the poor man had no instructions. I don't think he would have lied."

The shah said Maj. Gen. Robert E. Huyser, the deputy commander of U.S. forces in Europe who was dispa tched to Tehran by the white House, undermined the caretaker Cabinet the shah left behind by arranging a meeting between the Army chief of staff, Gen. Abbas Gharabaghi, who was nominally loyal to the shah, and Bazargan, who was trying to replace it.

After the shah left the country, "Huyser prevented the Army to preserve the constitution. And the Army gave up for this ridiculous man Bazargan who was just an Anglo-American puppet." Bazargan served as the first prime minister under Khomeini; but his government collapsed when the American Embassy was seized.

Pahlavi also sharply dismised current American policy in the Persian Gulf, describing as "ridiculous" plans for a rapid deployment force that would use prepositioned equipment in the area. "The United States has two airborne divisions to place against 13 Russian airborne divisions in the area. aYou are stockpiling equipment to bring 15,000 Marines that it will take two or three days to fly here, while the Russians could send 400,000 troops into my country immediately. If I stayed in my country, I would have had 600,000 troops to use in such a case. In 1983 it would have been 760,000 troops."

The shah added that he had "warned the United States about 12 years ago, America and the British, on Afghanistan and, as usual, the U.S.A. thought that America knew better and took my warning not very seriously. Then there was the series of coups in Afghanistan until they officially proclaimed a Marxist government. If I had been in my country and continued our policy, now and especially in 1983 we would have been better off. cNothing outside of a world war could have pushed down through Baluchistan down to the [arabian] Sea or Indian Ocean. Now, what you have is that even the Islami conference in Islamabad said that their profound belief is that the Soviets should withdraw their troops and they are going to contract the present government of Mr. [babrak] Karmal. That means they are recognizing the Afghan government. Who knows how many Europeans will do the same? They will say that there is only a political solution to this problem. I'm not urging war, mind you, I'm not saying that. But I'm just saying that everyone will accept the fait accompli, you will see, as usual."

As he has done before, the shah blamed much of the turmoil in Iran on the rapid pace of economic and social change under him that he said brought yearly per capital income from $60 to $2540 in a decade. He contrasted the rapid expansion of the work force during the rule to the 4 million people he said were now unemployed. "Eventually, we went faster than some people could digest," he added.

"It is not my person that matters," he said. "We are all coming and going.

But it is my country and what we were trying to build that matters. It takes 100 years for a tree to grow and only a minute for them to cut it. They are destroying the forests, even. They are destroying everything.

"We were thinking of the great civilization. We were thinking life could be enriched by art and by spirit, but the blossoming of thought and the spirit. And now it is all destroyed," the desposed shah said in the gathering darkness of the Kabbeh Palace.