Thirty years to the day after the murder of the Rev Martin Luther King, the life and death of the youngest recipient of the Nobel Peace Prize still haunts an America where his dream of racial justice has not been fully achieved.

King was 39 when he was shot dead on the balcony of the Lorraine Motel in Memphis by James Earl Ray, although this week Coretta Scott King repeated the family's doubts about who killed her husband. The southern city where he was killed hopes to attract thousands of people to three days of commemorations this weekend marking King's life, death and achievements.

The weekend's events include a commemorative service at the church where King preached his last sermon with the famous words: "I've been to the mountain top". A two-mile march will retrace the steps King and others took with the striking garbage workers he was supporting and a candlelight vigil will be held in the courtyard of the Lorraine Motel.

King is hailed variously as an advocate of non-violence, martyr or a myth. His admirers and his critics still have trouble finding language strong enough to describe him. One of his biographers, Taylor Branch, says the black Baptist pastor represents the "best and most important metaphor for American history in the watershed post-war years".

At the end of the 1963 civil rights march on Washington, the high point in the civil rights struggle, King spoke movingly of his dream of a racially united nation. A year later, at the age of 35, King received the Nobel Peace Prize and Congress approved the Civil Rights Act. The Voting Rights Act was passed the year after.

King was considered too militant by conservative blacks and too timid by more radical leaders like Malcolm X. The FBI subjected him to telephone taps, blackmail and threats, and one FBI report described him as the "most dangerous Negro to the future in this nation".

After King met Pope John XXIII, J. Edgar Hoover said: "I am amazed that the Pope gave an audience to such a degenerate."

Thirty years later, what is King's legacy to the US and to the world?

"Things are a lot better now,' said Taylor Rogers, who was one of 1,300 striking workers King came to help in Memphis in April 1968. The lot of the workers did improve in ensuing years, says Mr Rogers, but he believes King would "not be fully satisfied today . . . He would see the progress that has been made and would want to see people a little more close together than what they are."

Thirty years on Memphis is a city with a 62 per cent black population, the third-largest in the US, as well as a black mayor and five blacks among the 13 members of the city council, including its chairman, but in the US, where the po lice beating of Rodney King and the verdict of the O.J. Simpson jury point to a country that still suffers from many deep racial divides, there is contrasting evidence about the degrees of progress towards King's dream.

A recent report from the Milton S. Eisenhower Foundation concluded that the existence of two unequal societies predicted 30 years ago happened and was getting worse. A recent CBS News poll found that 40 per cent of whites but only 30 per cent of blacks believed that race relations would be better in the coming century.

Cities throughout the US continue to struggle with spending imbalances that all too often produce a two-class public school system.

Although blacks account for 12 per cent of the population, within two years they will account for half of all AIDS cases in the US. Young black men die violent deaths in numbers heavily disproportionate to whites and are an equally disproportionate part of the prison population.

In one of his last sermons, King expressed the fear that his dream at the Lincoln Memorial in 1963 had started to "turn into a nightmare". Yet there are encouraging signs of greater moves towards equality in the US.

Stephan and Abigail Thernstrom, in their book America in Black and White: One Nation, In- divisible, catalogue progress in black-white relations and report that a third of all blacks now live in the suburbs. There is much to do, they said in a recent Wall Street Journal essay, but also "much progress".

Apart from his leading role in the civil rights movement, King is also remembered today for his commitment to non-violence and his refusal to allow his faith and his political idealism to be separated.

In his last Christmas sermon in Ebenezer Baptist Church in Atlanta, Georgia, King said: "The very destructive power of modern weapons of warfare eliminates even the possibility that war may any longer serve as a negative good."

A few weeks earlier King said the Vietnam war had made the US government "the greatest purveyor of violence in the world today".

King's opposition to the war alienated the Johnson administration and the White House. A New York Times editorial argued that "Civil Rights and Peace don't mix", and Life magazine claimed King had gone "beyond his personal right to dissent" when he linked his demands for civil rights with his condemnation of the war.

None of this anger was visible earlier this year when all the cardinals of the US condemned the possibility of the US engaging in a war at the height of the Gulf crisis. Part of King's legacy has been the ability of church leaders today to speak out on issues of justice and peace without fear of condemnation for mixing religion and politics.

In South Africa, King's non-violence also inspired church leaders in their resistance to apartheid.

Shortly after King's murder, the South African Council of Churches found itself in a new phase of conflict with the apartheid regime. The publication of the SACC's Message to the People of South Africa drew a reaction from John Vorster which had been received by no previous theological document.

Vorster warned against church leaders who "wish to disrupt the order in South Africa under the cloak of religion". He went on to warn clerics who were planning to "do the kind of thing here in South Africa that Martin Luther King did in America" to "cut it out, cut it out immediately, for the cloak you carry will not protect you if you try to do this in South Africa".

Vorster met an instant and stiff reply from the Anglican Primate and president of the SACC, Archbishop Robert Selby-Taylor, and other leading clergy, including Bishop Bill Burnett and the Rev Beyers Naude.

The churches were set on a collision course in South Africa. Younger clergy, including the future Archbishop Desmond Tutu, the Rev Allan Boesak and the Rev Barney Pityana, would assume the mantle of King and ensure that King's legacy today would include the contribution his principles of non-violent direct action made to ending apartheid.