JOHANNESBURG, JUNE 19 -- The shadowy South African Communist Party, after 40 years of underground life, announced today that it is going public and relaunching itself as a legal organization starting next month.

Joe Slovo, the party's general secretary, told a press conference here that the party leadership had decided to celebrate the occasion by holding a mass rally in the black township of Soweto outside Johannesburg on July 29, at which time the party's secret leadership would be partly disclosed.

Slovo conceded that the decision to relaunch the party had come at "a complex moment in the international situation," a reference to the Communist parties in Eastern Europe, where, he noted, "socialism is in crisis {and} has suffered some severe setbacks."

The revival of the Communist Party here marks a milestone in the long, difficult history of the party since its formation in 1953 following dissolution of the original Communist Party of South Africa, which had been organized in 1921 but banned under the Suppression of Communism Act of 1950. The party was forced to go underground and merge most of its anti-apartheid activities with the African National Congress.

As a result of this strategy, Communist Party officials took over important roles in the ANC's armed struggle and on its National Executive Committee. Slovo, a Lithuanian-born white, was for a long period the ANC's head military strategist and chief of staff of its military wing, Umkhonto we Sizwe (Spear of the Nation).

It was not immediately clear how the unveiling of the Communist Party would affect its longstanding alliance with the ANC. Slovo said the two organizations had what he called "non-hostile, non-antagonistic and non-competitive differences."

Slovo said it was still too early to speculate what might happen in the event of a general non-racial election in South Africa, in which the Communist Party might run its own candidates separately from those of the ANC.

Responding to accusations in the South African press that the Communist Party has behaved like "a conspiracy," Slovo said it had never intended to emulate the highly secretive Broederbond, or Brotherhood, of Afrikaners who used that organization to infiltrate and control the white government for decades.

"The banning of our organization led to the obvious result that most of our membership was secret," Slovo said.

Slovo said the Communist Party would work toward complete openness concerning its membership and policies in the future. But, Slovo said, because the process of democratization in South Africa is still subject to change, the party will maintain an underground organization, and members of its externally based central committee "will not be known publicly, not all of it."