Platinum prices could rise from this week's 23-year high, an Implats spokesman has said, but such an increase may harm the metal's long term prospects on the international market.

Jewellery buyers were troubled by the hike on Wednesday that saw prices go up to $712 an ounce, while carmakers are increasing their efforts to ration their use of the material.

Implats marketing executive Derek Engelbrecht said 'I think there's some more upside, but we'd prefer to see it a bit lower. We'd be happier with prices around $650 to $675.'

The current price represents a jump of $100 since the beginning of the year, and of 70 per cent since late 2001. Demand for Chinese jewellery, in particular, is said to have suffered as a result.

Worldwide platinum demand for jewellery is, Implats estimates, going to decline from last year's figure of 2.85 million ounces to 2.67 million ounces, with automotive use dropping from 2.6 million to 2.46 million ounces.

Carmakers are increasingly feeling moved to buy palladium, which at $200 an ounce is much cheaper than platinum.