Willem Wijnstekers, secretary-general of the Convention on International Trade in Endangered Species (CITES), called for a simpler system as delegates from 166 countries gathered for the latest meeting in Bangkok.

CITES, signed 31 years ago, is the biggest and most successful treaty regulating the lucrative wildlife products industry and is responsible for the 15-year ban on the international ivory trade.

"It is appropriate for me to once again ask for your cooperation to help solve what I believe has been and still is a major problem with CITES: overcomplication," said Wijnstekers in a newsletter released ahead of the conference.

"I have reiterated the view that CITES has become too complicated to implement and enforce... in many cases it is totally unclear why we have complicated things so much and what the conservation benefits of certain measures are today."

The system provides trade protection for species threatened through over-harvesting, pollution and habitat destruction.

The convention places 5,000 animal and nearly 29,000 plant species in one of three categories that range from a ban on international trading to allowing limited selling through a series of permits and quotas.

Wijnstekers said some of the regulations had become unwieldy and, in the newsletter published in July, urged those gathering in Bangkok to "imagine for a while being a Customs officer who has to apply them".

Excluding commercial fishing, the international trade in wildlife is worth billions of dollars annually and covers more than 350 million plants and animals every year, according to CITES.

The meeting of its top decision-making body in Bangkok, from October 2 to 14, will scrutinise some 50 proposals to change trade rules for species from the great white shark and elephants to orchids and ramin timber.

The CITES meeting is expected to witness fierce debates over whaling and the ivory trade.

Illegal smuggling threatens to tip some species into extinction and conservationists have demanded better policing by governments and law enforcement groups worldwide.

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