JOHANNESBURG, SEPT. 11 -- African National Congress leader Nelson Mandela said today that the government's failure to halt black factional fighting in townships near here is endangering the effort to negotiate a new political system for South Africa. Fighting raged in a half-dozen townships today, with 34 people reported killed.

Mandela met with President Frederik W. de Klerk over the fighting. Mandela said he told the president that if the killing did not stop soon he might have to reverse his suspension in June of the ANC's armed struggle against the government's apartheid system of racial separation. The ANC has said white extremists are fanning tribal fighting to disrupt the negotiating process and that police do little to stop the extremists.

Mandela said he was finding it increasingly difficult to resist demands from his followers that the ANC's guerrilla wing be reactivated to defend them from attackers.

To resume the armed struggle, Mandela conceded, would be a serious setback to the negotiating process between the ANC and the government. "There is no doubt that the peace process is in distress," he said.

The violence has pitted Zulu tribe members loyal to Chief Mangosuthu Buthelezi against supporters of the ANC, who largely are members of the Xhosa tribe. The ANC also accuses the police of siding with Buthelezi's Inkatha Movement in attacks on the ANC, both in Natal province, where the two groups have fought a virtual civil war for four years, and in the six weeks of fighting in the Johannesburg area.

The violence Monday night and today flared from one township to another and seemed to be mostly between Zulu supporters of Inkatha, who are migrant workers from Natal living in large men-only hostels, and residents of the townships, most of whom back the ANC. The deaths reported today brought the total in the recent fighting to more than 700.

A battle between hostel-dwellers and residents in Kathlehong, southeast of Johannesburg, raged overnight, leaving 20 dead, according to a police body count this morning. Another man was killed in adjoining Thokoza and three in nearby Vosloorus, according to a police report, which gave no details.

Farther west, in Ennerdale, a crowd protesting high rents went on the rampage after police dispersed them with tear gas. They burned down the civic center and a nearby shopping complex.

In Soweto, another nine bodies were found today following weekend fighting in which 33 people were killed.

Other killings occurred in trains. Tribal groups said to be Inkatha supporters hacked commuters with machetes and threw some from moving coaches. Several people jumped from the trains to escape the attackers and were injured.

One body was flung under a bridge in downtown Johannesburg this morning, and commuters were shocked at seeing blood-splattered railroad cars pull into the city's main station.

In another incident, a bomb demolished a Johannesburg cinema showing a movie titled "How to Make Love to a Negro Without Tiring" as part of a current film festival. No one was injured.

Mandela led a delegation of 22 members of the ANC and its allied organizations to the meeting with de Klerk, which focused primarily on the violence in Natal province, where more than 4,000 people have died in fighting between Inkatha and ANC supporters over the past four years.