President Carter was embroiled in a new controversy yesterday over an assertion that GOP presidential candidate Ronald Reagan might, as president, lead the nation into war.

Early in the day, Jody Powell, Carter's press secretary, characterized as an "overstatement" the president's assertion Monday night that the November election will decide "whether we have peace or war." But as the day wore on, Carter and Powell returned to the theme that the election of Reagan would increase the risk of war, as the president called on the former California governor to explain his "repeated habit" of suggesting the use of military force abroad.

Reagan responded angrily, calling the president's statement, "unforgivable" and "beneath decency."

The long-distance debate between the two major-party presidential candidates was the latest turn in the campaign of invective that has characterized the early weeks of the general election campaign. Both sides seemed to believe the exchange would work in their favor.

The episode began Monday night, when Carter, in a speech to the California AFL-CIO, said the November election will decide "whether we have peace or war."

Asked about Carter's charge, Reagan said yesterday morning, "I think it is inconceivable that anyone, particularly a president of the United States, would imply that . . . any person in this country would want war. And that's what he's charging, and I think it is unforgivable."

Later, addressing an airport audience in Pensacola, Reagan departed from his text to take issue with descriptions of him as "the fella who wants to take us into war."

"First of all I think to accuse that anyone would deliberately want a war is beneath decency," Reagan said with evident emotion. "I have two sons, I have a grandson, I have known four wars in my lifetime and I think like all of you that world peace has got to be the principal theme of this nation. And world peace can be obtained only by maintaining a strength that will keep any potential adversary from ever challenging this nation."

And responding to reporters' questions before addressing a fairground rally at Springfield, Mo., Reagan denied that he had ever advocated the use of military force. He was asked about Carter's statement that he had a "habit" of calling for the use of arms in danger situations and replied, with a trace of anger: "You fellas have heard everything I've said. Have you ever heard me say that? I'll bet none of you ever have, because I've never said it."

Carter said yesterday morning in a television interview that he had not meant to suggest that Reagan would deliberately seek to embroil the country in war, and Powell said the Monday remark was an overstatement of the president's main campaign theme that the election represents "two futures" for the country.

But Carter immediately returned to the theme during the same interview, calling for Reagan to explain his "repeated habit" of suggesting the use of U.S. military power abroad.

"I think in eight or 10 different instances in recent years he has called for the use of American military force to address problems that arise diplomatically between nations," Carter said in the interview.

"I don't know what he would do if he were in the Oval Office, but if you judge his past highly rhetorical calls for the use of American military forces in these altercations, it is disturbing."

If anything, the president's swift counterattack and later statements by Powell suggested that Carter strategists have been hoping to goad Reagan into some kind of reaction on the peace issue so that they could challenge him to explain a list of previous statements compiled by the Carter campaign organization.

Powell later issued a list of statements attributed to Reagan in which the Republican nominee had suggested the use of military forces in reponse to diplomatic problems around the world.

The president has been using the "two futures" theme since the beginning of his campaign and has accused the GOP nominee of planning to set off a "massive nuclear arms race" with the Soviet Union that would jeopardize world peace. But Reagan did not react strongly to those repeated suggestions that his election might mean war until Carter's speech Monday night to the AFL-CIO convention.

Word of the Reagan reaction reached the White House traveling party yesterday morning in San Jose. Calif. At the airport before flying to Portland, Powell boarded the chartered airplane carrying reporters and gleefully began reciting a list of what he said were previous Reagan statements suggesting U.S. military involvement abroad.

The list, compiled from newspaper clippings, included Reagan quotes on a number of international disputes between 1968 and 1980, including his suggestion last January that the United States "surround the island of Cuba and stop all traffic in and out" in response to the Soviet invasion of Afghanistan.

Other examples cited by Powell included:

Reagan's suggestion that in reponse to the Ecuadorian seizure of U.S. tuna boats in 1975 that the U.S. government send along a destroyer with the tuna boats.

A statement from Reagan saying he would have sent troops to Lebanon during the 1976 civil war.

Reagan's statement that he could not "understand for the life of me" why the government had not given the North Koreans an ultimatum to release the USS Pueblo or face military action.

Powell also said Reagan had suggested a military presence in Cyprus and an ultimatum to the Soviet Union to get out of Angola or run the risk of having to confront U.S. forces.

"It is about time that the Republican candidate stopped complaining about statements made by the president and address himself in a serious fashion to his record and the statements he has made," Powell said. "We have absolutely no apology for raising that issue and for asking Gov. Reagan to explain the numerous occasions when he has advocated the use of American military force."

Powell added:

"Gov. Reagan's statements over the past several years do raise serious questions about his judgements in handling international crises involving questions of war and peace."

Carter was equally unbending in his interview with television station KNBC in Los Angeles. Asked directly whether he would consider a Reagan presidency a threat to peace, he replied that he will let the public analyze Reagan's past statements and decide for itself.

"I'll let you examine what he has called for," the president said. "I've outlined it in general terms. But the record is there, to call for the use of military forces in a very dangerous situation has been a repeated habit of his as governor and as a candidate for president. What he would do in the Oval Office I hope will never be observed by the American people."

Reagan's response to Carter's statement was viewed as both an opportunity and a potential liability by his campaign staff.

One strategist said the president had blundered as the Reagan team believes Carter did a week ago in Atlanta when he suggested that Reagan was injecting "stirrings of hate" into the campaign.

Carter subsequently denied that he was accusing Reagan of being a racist and said that he did not believe that his opponent had injected racism into the campaign.

"This is another gaffe," said a Reagan strategist in reference to Carter's most recent statement."It's a reflection of Carter's mean streak."

But another Reagan aide acknowledged that the Republican presidential nominee could cause himself political damage if he kept reacting to Carter instead of concentrating on his own campaign.

Yesterday, for instance, the Reagan response to Carter's statement Monday diverted news coverage away from a long, philosophical speech Reagan gave a Louisana State University on "securing our freedoms." It was supposed to be Reagan's major news event of the day.

The LSU speech had few applause lines. It effectively quieted an initially enthusiastic sign-waving audience of several thousand young people assembled in an auditorium on the Baton Rouge campus.

But the crowd came alive when someone in the audience shouted, "No hostages," and Reagan responded, "That's right." He went on to cite the holding of the U.S. hostages in Iran as "an example of what is wrong with the foreign policy of this administration."

Reagan did not mention Carter's latest charge in his LSU speech. That was left to the man who introduced him, Republican Congressman Henson Moore, who accused the president of making "slanderous" and "vicious" statements about Reagan.

Despite the danger of Reagan being focused away from his own campaign, the emerging view on the GOP nominee's campaign plane is that the president is likely to lose more than he will gain in the exchange.

"In no way has Gov. Reagan been warlike, in no way has he advocated the use of force," said spokesman Lyn Nofziger. "The one reason he wants an adequate defense establishment is to maintain peace. There is bound to be a backlash from this constant slandering of the governor's motives and intentions."

Reagan's own rhetoric on some issues is also getting tougher, but he has been careful since a Labor Day blunder linking Carter to the Ku Klux Klan to talk about the administration record rather that about the president personally.

Vice President Mondale, campaigning yesterday in New York and Wisconsin, defended the president's suggestion that the Carter administration was "more likely to keep the peace" than a Reagan administration.

Responding to questions at news conferences in Rochester, N.Y., and La Crosse, Wis., Mondale said that in the last 12 years Reagan had proposed sending forces into eight or nine countries to protect American interests.

"Contrast that with a president who is both strong and peace oriented . . ."

and you find "we are more likely to keep the peace."

But GOP vice presidential candidate George Bush accused Carter of taking a "low road of misrepresentation and sly innuendo" in his sharpest attack yet on the president's campaign style.

In remarks to a Joilet, Ill., community college audience, Bush said, "The idea was if you voted for him [Carter] then you get peace, and if you voted for Gov. Reagan, you're apt to get war. I don't believe the American people are going to buy that kind of insinuation."

Later, in remarks prepared for a Republican fund-raiser in Lansing, Bush sharpened his attack and called Carter's statement "yet another case of this president engaging in a demagogic, irresponsible attack on his opponent." Bush said that if "Mr. Carter genuinely believes that peace or war is the terrible choice facing the American people," then Carter should have participated in the Sunday night presidential debate in Baltimore.