PRETORIA, SOUTH AFRICA, AUG. 1 -- Talks aimed at ending South Africa's apartheid system are back on track after a three-hour crisis meeting today between President Frederik W. de Klerk and Nelson Mandela, deputy president of the African National Congress.

The talks came under threat last week when police reported to de Klerk that they had uncovered a plot by the newly legalized South African Communist Party, an ally of Mandela's ANC. The police said the Communists intended to launch an armed insurrection to overthrow the white-minority government if the talks broke down.

Conciliatory statements by both leaders tonight made it clear that the next round of "talks about talks" between the two sides would go ahead Aug. 6 as scheduled.

The police report to de Klerk last week was accompanied by the detention of between seven and 12 Communist Party members, including Mac Maharaj, who is also a senior member of the ANC's national executive committee.

After the report and arrests, de Klerk summoned Mandela to his office July 26 and demanded that Communist Party leader Joe Slovo be dropped from the ANC delegation for the Aug. 6 talks.

The dispute appeared to deepen Sunday when Slovo, who also holds a high post in the ANC, told a Communist Party rally in Johannesburg that his passport proved he had not been in the country at the time the alleged plot was supposedly hatched. Slovo also countercharged that white extremists in the security establishment had fed de Klerk false information to derail the talks.

At the same rally, Mandela backed Slovo's disclaimer and made it clear he would not drop him from the ANC's five-member team chosen to meet with the government Aug. 6.

The rally statements were seen here as having placed de Klerk in an awkward situation in which he had no valid grounds for continuing to demand Slovo's removal, but would lose more support in his own conservative white constituency -- which already is unhappy about his bold reformism -- if he appeared to back down and accept him.

However, after today's meeting, Mandela issued a statement indicating that he had been at fault for believing that de Klerk wanted Slovo dumped. There had been a "misunderstanding," he said, "as a result of which I thought the state president had demanded that Joe Slovo be excluded from the delegation of the ANC."

"The correct position," Mandela said, "is that the state president was disturbed by evidence placed before him of statements and actions which went against the spirit" of the first round of talks between the government and the ANC in May.

Some observers, noting that Mandela's statement did not square with reports from ANC and government officials that de Klerk had wanted Slovo out of the negotiations, believe that Mandela was trying to save face for de Klerk. The observers say that Mandela's statement gives a glimpse of the extent to which he and de Klerk are working together, despite apparent conflicts.

Mandela's statement expressed the "total commitment" of the ANC, of the Communist Party and of the ANC's guerrilla wing to the negotiating process. He also said there would be a "personal undertaking" that agreements between the two sides would be strictly adhered to in the future.

Mandela's statement seemed to indicate that he was prepared to crack down on the rhetoric of some ANC members, notably guerrilla leader Chris Hani, who have continued to use revolutionary language and slogans since the talks began.

In a statement issued a few hours after Mandela's, de Klerk said that in view of the ANC leader's undertakings, the government was prepared to go ahead with the Aug. 6 talks.

However, de Klerk said, "I made it clear that statements and actions by prominent ANC members, as well as by SACP {South African Communist Party} members, which militate against the wording and spirit of the {previous talks}, seriously jeopardize the continuation of discussions aimed at the continuation of a climate for discussions," de Klerk said.

Neither leader made any reference to the arrest of Maharaj or the other SACP members.

In another development aimed at lowering political tensions, the government announced Tuesday that it had disbanded a controversial branch of its armed services, called the Civil Cooperation Bureau, which has been accused of operating hit squads and "dirty tricks" units.