The group presented its findings at The Hague meeting of the Convention on International Trade in Endangered Species (CITES), widely credited with stemming the slaughter of the African elephant by imposing a ban on international ivory trade in 1989.

The ivory trade came to a virtual halt after the ban, but has since revived. Experts say the killing of elephants for their tusks, mainly in central Africa, has reached levels not seen since 1989 because of Asian-run crime syndicates.

China, Japan and Thailand, where possessing ivory objects is a matter of prestige, are the most important markets for illicit shipments from Africa, wildlife trade monitor TRAFFIC said in a report last month.

Care for the Wild International, which worked with ivory trade experts Esmond Martin and Daniel Stiles, said illegal worked ivory was imported into the United States by individuals and through the Internet.

The retail outlets surveyed offered 23,741 ivory items for sale, originating mainly in China but also in Japan.

Most of the illegal jewellery, netsukes and human figurines entered the United States mislabelled as antiques, mammoth ivory or bone, whose trade is allowed there, the report said.

Martin told reporters in The Hague that it was very difficult to give an estimate of the size of the illegal ivory trade in the United States or elsewhere.

Care for the Wild International joined other environmental groups in their calls on CITES to reject any proposals at its June 3-15 meeting to loosen the ivory trade.

"If the United States with its financial and technical resources cannot prevent illegal trade, then who can," said Barbara Maas, executive director of the conservation group.

"It's not safe to loosen ivory trade ... Poaching has alarmingly increased. Don't make it any easier," Maas said.

Elephants will trigger a lot of controversy at CITES. African countries are split over protecting the elephant, some saying elephant populations have grown at an unsustainable rate.

Botswana and Namibia want looser conditions on ivory sales from southern African countries, but Kenya and Mali seek a 20-year moratorium on sales from those states to cut poaching.