American hunters are emerging as a strong and growing threat to the survival of African lions, with demand for trophy rugs and necklaces driving the animals towards extinction, a coalition of wildlife organisations has said.

Demand for hunting trophies, such as lion skin rugs, and a thriving trade in animal parts in the US and across the globe have raised the threat levels for African lions, which are already under assault because of conflicts with local villagers and shrinking habitat.

"The African lion is a species in crisis," said Jeff Flocken of the International Fund for Animal Welfare. "The king of the jungle is heading toward extinction, and yet Americans continue to kill lions for sport."

Two-thirds of the lions hunted for sport were brought to America over the last 10 years, a report released by the coalition said.

The organisations, which include IFAW, the Humane Society of the United States, Humane Society International, Born Free and Defenders of Wildlife, called on the White House to ban the import of lion trophies and parts by listing the animals as endangered species.

The number of wild African lions has fallen sharply in the last 100 years, the organisations said. A century ago, as many as 200,000 roamed across Africa. Now, by some estimates, fewer than 40,000 remain in the wild; others put the figure for survivors at 23,000, and they have vanished from 80% of the areas where they once roamed.

Lions have become extinct in 26 countries. Only seven countries – Botswana, Ethiopia, Kenya, South Africa, Tanzania, Zambia and Zimbabwe – are believed to contain more than 1,000 lions each, according to the Panthera conservation group – which is not part of the coalition making the appeal.

The single biggest threat by far to the animals' survival is humans, though not necessarily western hunters. "It is just the very, very widespread killing of lions, mostly in a conflict situation, by anyone who is trying to farm livestock in Africa and finds it very difficult to co-exist with lions," said Luke Hunter, the executive vice-president of Panthera.

There is also a lot of pressure on lion habitats with wilderness areas shrinking to build roads – such as the controversial highway across the Serengeti – or to make room for agriculture.

But the report by the wildlife coalition, filed with the White House on Tuesday, said western hunters were a growing danger to the lions' survival.

Between 1999 and 2008, 64% of the 5,663 lions that were killed in the African wild for sport ended up being shipped to America, it said. It also said the numbers had risen sharply in those 10 years, with more than twice as many lions taken as trophies by US hunters in 2008 than in 1999. In addition to personal trophies, Americans are also the world's biggest buyers of lion carcasses and body parts, including claws, skulls, bones and penises. In the same years, the US imported 63% of the 2,715 lion specimens put up for sale.

For some countries, including Tanzania, Zambia, Namibia and Mozambique, hunting for sport was the main threat to the lions' existence. But even in countries which did not attract large numbers of tourists on hunting trips, the practice was taking a growing toll.

The conservationists noted that hunters' penchant for bagging a male lion risked wiping out entire prides. The loss of the alpha male could set off a struggle for supremacy among the survivors that could lead to further deaths of adult male lions, or male cubs seen as potential threats.

A hunting ban, the conservationists said, would reduce that threat by taking Americans out of the game. It's one of a range of threats to the survival of the species, said Teresa Telecky, director of wildlife for Humane Society International. "But what is most certainly true is that of all the threats to the African lion, the one we can best address here in this country is their import."

Flocken noted that all of the other big cats are protected – jaguars, leopards and tigers. "African lions are the only ones left out there," he said.

However, other wildlife experts argued that a total hunting ban was a "nuclear option". They said responsible hunting could in some cases help conserve populations by maintaining wilderness areas. Existing US and international regulations, such as the Cites conventions against trafficking in endangered species, could also be reinforced to protect lions, they said.

"If you remove hunting, the very real risk is that you force African governments to generate revenue from that land and the obvious thing is cattle and crops which just wipe out habitats," said Hunter.