The arrests of 23-year-old twins
Brandon-Lee and Tony-Lee Thulsie earlier this month were the first in South Africa relating to alleged IS membership.
“Both the defence and the state were not ready to proceed, hence the trial was postponed until July 25, ” National Prosecuting Authority spokeswoman Phindi Louw told reporters outside Johannesburg magistrates’ court.
“We have reasonable and probable cause to believe that an offence was committed .”
Police last week said the pair were suspected of planning to bomb the US embassy in Pretoria as well as unspecified Jewish facilities.
They are also alleged to have attempted to travel to Syria to join IS.
The brothers waved to family members in court after the short hearing.
The United States and Britain warned last month of the possibility of imminent attacks by jihadist extremists in South Africa’s major cities.
Muslims account for 1.5 percent of South Africa’s 53 million people. The country has so far been spared the jihadist attacks that have struck several other countries on the continent.