In a change of direction, the 171-nation Convention on International Trade in Endangered Species (Cites) plans to wade into commercial issues as never before, hoping to intervene before the survival of a species is under serious threat.

Until now, Cites - a treaty that went into force in 1975 - has stepped in 'at a far too late stage, when the species were already or almost commercially extinct', said Cites secretary-general Willem Wijnstekers, referring especially to timber such as mahogany.

The ongoing struggles to control elephant poaching and protect tigers from extinction are also on the conference agenda.

The meeting will consider a European proposal to regulate trade in the spiny dogfish, a small shark exploited for the fast-food business, and in the porbeagle, another shark valued for its meat and fin. Both sharks grow slowly, mature late and have few young.

Another proposal would help protect sawfish. These fish with famously serrated snouts are popular aquarium items and are also exploited as food.

The United States and Canada, which are among the world's top three exporters of spiny dogfish, have signalled that they may oppose the proposal, as has New Zealand, said Ms Sonia Fordham of Oceans Conservancy in Washington.

Proposals need a two-thirds majority of voting countries. Non-governmental organisations may present papers, speak at meetings and lobby delegates, but cannot vote.

'We have got a tough battle ahead of us. We think it is still winnable, but the sharks will be one of the biggest battles of the conference,' said Ms Carroll Muffett of the Greenpeace environmental movement.

'This is about more than sharks. It is about the future of commercially valuable fisheries within Cites.'

The conference will also consider listing Spanish cedar, a tropical hardwood from South America prized for its salmon-coloured wood that is used to make cabinets, musical instruments and the aromatic lining of cigar boxes.

Conservationists say loggers are stripping national parks and protected areas in several countries, especially Peru.

Other proposals would limit trade in the wood of the brazilwood tree, from which high-end bows are made for stringed instruments. Protection also would be increased for several species of gazelles.

Cites lists more than 7,000 animals and 32,000 plants whose trade is regulated, including about 800 highly threatened species that are banned from commercial trade without special licences.

ASSOCIATED PRESS