Justice Minister Kobie Coetsee indefinitely postponed the execution of the "Sharpeville Six," lifting a court-imposed deadline for a final judicial appeal to save the condemned blacks from the gallows.

Coetsee also sought Tuesday to silence those campaigning against the convictions of the six and appealing for clemency, saying pressure "can serve no purpose and may only serve to obstruct the course of justice."Canceling a July 19 deadline on a final petition to Chief Justice P.J. Rabie, Coetsee said the five black men and a woman must "be afforded the opportunity of exhausting the remedies which the law offers."

Paul W.J. Human, the trial judge who sentenced the six to death by hanging in December 1985 for their part in the 1984 mob killing of a black official, set the deadline at a June 13 appeal hearing.

Human refused defense lawyers' pleas to reopen the trial on the basis of perjured evidence by a state witness, but gave the defense until July 19 to challenge his ruling with the Chief Justice at the Appeal Court, South Africa's highest judicial body.

The defense has asked Rabie to allow a full appeal hearing on reopening the case, citing alleged tainted evidence against the six given under police pressure by key witness Joseph Manete.

Attorney Prakash Diar, spokesman for the defense team, Tuesday said Rabie has not yet ruled on the petition.

If the appeal is denied, Diar said the defense will ask President Pieter W. Botha for clemency.