"I call it the madman theory, Bob. I want the North Vietnamese to believe that I've reached the point where I might do anything to stop the war. We'll just slip the word to them that `for God's sake, you know Nixon is obsessed with Communists. We can't restrain him when he's angry' . . ."

From what we now know, US President Richard Nixon was describing with some accuracy his state of mind when telling aide Bob Haldeman how he intended to carry out his 1968 election promise to "end the war and win the peace".

Nixon did try almost everything, without restraint and without success, to stop the North Vietnamese winning a war in which 58,183 US service men and women lost their lives, and which has left deep scars on the psyche of both the United States and Vietnam.

Those Americans opposed to "Nixon's war" back then included a long-haired, draft-dodging Rhodes scholar, who today arrives in Hanoi as the first serving US President to visit Vietnam since the fall of Saigon, now called Ho Chi Min City.

It has fallen to President Bill Clinton to "win the peace" a quarter of a century after that ignominious final retreat from the roof of the US embassy. The end of the war in 1975 left the US and Vietnam in a state of bitter non-belligerence.

After he took office, Mr Clinton worked hard for reconciliation with Hanoi. He lifted a punitive trade embargo in 1994, established diplomatic relations in 1995, and in July this year signed the first trade agreement between the two countries.

Now he arrives in Hanoi on something of a personal pilgrimage to lay the ghosts of that conflict.

Before leaving Washington he announced that one of the conditions for a mutual improvement of relations, in fact the issue of "highest priority" for the Americans, was recovering the bodies of MIAs, the 1,498 US personnel still listed as Missing in Action.

The young man from Arkansas who made sure he avoided fighting the Vietnamese will this weekend, therefore, visit the site near Hanoi where a US aircraft crashed when bombing North Vietnam, killing the crew.

There are scores of such sites. The Pentagon says that during the war it lost 3,689 fixed-wing aircraft, many shot down by the North Vietnamese.

The US Government is paying $19 million (£18m) a year in Vietnam in a costly effort to try to find those Americans who never made it home. This is far in excess of the total of annual US humanitarian aid to Vietnam, which endured terrible consequences from the war.

Washington has the means and the will to continue the MIA investigations indefinitely, and for individual American families it is clearly a sacred mission.

But it must seem to the Vietnamese, who agreed to begin cooperating in the searches to end the US trade embargo seven years ago, that Nixon's obsession with Communists has been replaced with an American obsession with MIAs - especially given the scale of Vietnam's own losses which include 300,000 missing in action and over one million dead.

Nor is the American dedication to resolving the MIA issue matched by a similar level of concern for Vietnamese victims. This is a sore point for the Hanoi government, which argues that the United States should be doing more to help it deal with the continued suffering caused by the long-lasting effects of Agent Orange and the huge quantities of leftover US ordnance which kill and maim dozens of people every year.

More than 72 million litres of Agent Orange was sprayed over large areas of the countryside, causing massive suffering. But no financial redress has ever been offered to the Vietnamese, nor has the United States government done anything to help clean up contaminated areas.

American personnel and family members who suffered illnesses associated with the toxic defoliant have been compensated by the US government.

Hanoi claims that the poison still affects some one million people and has caused birth defects - including deformed or missing limbs - in up to 150,000 babies, and that this is continuing today. But Washington says the link between Agent Orange and the birth defects in Vietnam remain to be proved.

However, if Mr Clinton was to visit, for example, Tu Du Maternity Hospital in Ho Chi Minh City, he would find 40 children there suffering from physical and neurological disabilities which Vietnamese doctors say were caused by the dioxin in the defoliant.

The Vietnamese want the US to help provide healthcare and medicines, and send specialists to assess dioxin levels in the environment and people.

Le Cao Dai, executive director of the Vietnam Red Cross Agent Orange Victims Fund, has urged President Clinton to recognise that one million Vietnamese are victims and to provide financial assistance for clean-up operations.

There has been some suggestion that Mr Clinton should go further and apologise for American actions in the war, during which Viet Cong prisoners were often summarily executed by US soldiers. Having demonstrated against the war, he has the moral qualifications to do so. But US officials have said this will not happen.

The wounds in the United States are still too raw for the President to apologise. Many American veterans would ask what right he had to make that sort of judgment. Washington also has some concerns about human rights abuses in Vietnam, which make the question more complicated.

"He wouldn't have to apologise," said Chuck Searcy, a US veteran working in Hanoi with disabled children who lobbied hard for the Clinton visit. "He could simply acknowledge America's role in the suffering caused by the war."

Vietnam leaders see Mr Clinton as a "good American" who opposed the war. It was up to the United States to decide if an apology was warranted, but it depended on the thinking of the American people as well as its leaders, said former Prime Minister Vo Van Kiet, a 77-year-old former Viet Cong guerrilla.

This appreciation of Mr Clinton's position was matched by the US President's forward-looking remark last weekend: "In our national memory, Vietnam was a war, but Vietnam is also a country - a country emerging from almost 50 years of conflict, upheaval and isolation, and turning its face to a very different world."

For the Vietnamese the visit by Mr Clinton is in any case momentous. It means not so much a closure as an opening. It allows the two countries to get on with the dominant obsession of both capitals today, that of doing business.

Mr Clinton has brought with him delegations from 30 US firms. The US-Vietnam trade agreement signed in July should open the US market to Vietnamese goods and make it easier for American firms to do business in Vietnam.

The lapel pin being produced in a Hanoi factory to commemorate the historic visit says it all. It shows the American and Vietnamese flags side-by-side, exploding from the top of a Coca-Cola bottle.

Due to pressure of space, Brendan Glacken's Times Square has been held over but will appear tomorrow.