The fate of the gorillas has infuriated animal rights groups that want them sent back to their natural habitat.
Mary Fosi, a senior official at Cameroon's Ministry of Environment and Nature Protection, said South Africa had promised to return the gorillas, known as the Taiping Four after the Malaysian zoo where they appeared after being smuggled out of Cameroon in 2002.
"We are waiting now for the South African government to respect its engagement to bring back the gorillas to Cameroon by June 2005," Fosi said in Cameroon's capital, Yaounde, on Saturday.
The population of lowland gorillas, numbering several thousand in Cameroon, Central African Republic, the two Congos, Gabon and Nigeria, is rapidly declining because of hunting and logging, trading in pets and the deadly Ebola virus.
Activists say the apes should be returned under the Convention on International Trade in Endangered Species (CITES), which regulates the global trade in threatened wildlife.
The animals were discreetly taken to South Africa's National Zoo in Pretoria in April 2004 from Malaysia. Cameroon, South Africa and Malaysia are all party to CITES.
Fosi's comments came after the International Fund for Animal Welfare (IFAW) criticised South Africa's government for allowing preparations for placing the gorillas on display at the zoo.
Appeal for cooperation
"Given that Cameroon specifically asked South Africa for the return of the gorillas on two separate occasions, we feel the current situation shows a serious lack of respect for both CITES and the spirit of African cooperation," IFAW said on Thursday.
IFAW also criticised South Africa for failing to convene a technical committee to facilitate the gorillas' return.
Animal welfare groups want the gorillas sent to the Limbe Wildlife Centre in southwestern Cameroon. Fosi said facilities at the centre had already been upgraded for their return.
"The centre has successfully put in place a family group of gorillas and the Taiping Four will be integrated into the resident gorilla population," she said.