THE leaders of South Africa's three main political groups have vowed swift implementation of a historic accord to end the violence that is threatening political negotiations.The signing of the accord at a public ceremony in Johannesburg Saturday marked the first national agreement entered into between the ruling National Party, the African National Congress (ANC), and the Zulu-based Inkatha Freedom Party. It is also the first time that the government has attended a national conference convened and chaired by neutral parties - in this case, church and business leaders. Church leaders urged the political leaders to take the message of the accord into the community with rallies nationwide. "The miracle that is taking place here is one that is being undergirded by people in every part of the world," said Archbishop Desmond Tutu, head of the Anglican church in southern Africa, who conducted the closing prayer in four African languages as well as Afrikaans and English. The accord, which sets up mechanisms to resolve conflict and make the police accountable to the community, has left several key issues unresolved, including a clear definition of what constitutes a dangerous weapon and the future of the ANC's military wing, Umkhonto We Sizwe (Spear of the Nation). Political leaders worry that if the peace accord does not hold - and lead to full negotiations - the country could erupt in civil war. The right-wing Conservative Party boycotted the peace conference in a bid to force the government into holding another whites-only election before a nonracial constitution is introduced. At its annual conference in Pretoria, Conservative leader Andries Treurnicht said signing the accord would be the first step toward giving the ANC control of the security forces. Delegates called for rebellion against President Frederik de Klerk and threatened a campaign of violence. Mr. De Klerk told reporters after the accord was signed that he regretted the absence of the right wing, but was confident most right-wing supporters would eventually force their leaders to the negotiating table. The mood of compromise and reconciliation among the 300 or so delegates to the peace convention contrasted sharply with the militant note struck by 3,000 armed Inkatha supporters who surrounded the Johannesburg hotel where the ceremony was held. The signing of the 33-page accord followed six days of political violence in the black townships around Johannesburg, which appeared to be orchestrated to wreck the accord. Political scientists here say that the violence, which left 125 dead, was the work of a "third force." The violence was set off a week ago by three black gunmen who opened fire on a crowd of Inkatha supporters. The shootings were followed by indiscriminate reprisals on township residents and random attacks on train and bus commuters. The agreement aimed at stopping the killing was signed by the leaders of 23 political parties, trade union federations, and provincial governments. The militant Pan-Africanist Congress of Azania and related trade-union federations made pledges of peace, but said signing the accord would be tantamount to recognizing an illegitimate government. The accord, which follows three months of talks, establishes a framework for observing basic civil rights, provides for creation of a national peace committee to oversee community monitoring of security forces, and creates special courts to deal with political violence. De Klerk vowed the government would "scrupulously fulfill its responsibilities and will do everything in its power to ensure that the envisaged structures function properly." "My signature is not a formality," he said. "I accept this as a word of honor." ANC President Nelson Mandela said he was signing the accord despite serious reservations because the ANC accepted that "compromise is essential in an accord of this nature." "We are under no illusions that this accord is a magic wand," he said. "Our signatures alone cannot light the path to peace. De Klerk conceded that the accord was not perfect, and that it was essential the signing be followed swiftly by political negotiations on a new constitution. Inkatha's Chief Mangosuthu Buthelezi alone declined to speak before the accord was signed. After the signing, Chief Buthelezi, who had been skeptical about the accord, described it as "an instrument of God." Buthelezi defended the demonstration by Inkatha supporters, saying they dispersed peacefully. The demonstration - five hours pf chanting and war dances - was monitored by police in armored vehicles. At a news conference later, De Klerk, Mandela, and Buthelezi clashed over how the demonstration was handled.