The U.S. Fish and Wildlife Service, saying an analysis suggests African lions are in danger of extinction in the foreseeable future, has proposed listing them as threatened under the Endangered Species Act.

If the listing is approved, it would make it illegal for a U.S. citizen to engage in the sale of lions or lion parts across state or international borders, or to hunt or kill captive lions within the United States.

The prohibition against selling lions would not apply to zoos, the service said.

U.S. hunters would still be able to import, as trophies, lions they kill in Africa so long as the animals "originate from countries with a scientifically sound management plan for African lions," it said in a release.

The burden would be on each country to demonstrate to the USFWS that it had management plans in place and that it was enforcing quotas, the service explained.

While hunters from the U.S. account for most of the lions, rhinoceroses and elephants killed in Africa, sport hunting -- when properly monitored and regulated -- is not believed to be a serious threat to those species, it said.

Rather, especially in the case of lions, the major threats are increased conflict as lions come in contact with humans, habitat loss and lack of prey, said U.S. Fish and Wildlife Service Director Dan Ashe.

"The African lion -- a symbol of majesty, courage and strength -- faces serious threats to its long-term survival," he said.

"Listing it as a threatened species will bring the full protections of U.S. law to lion conservation, allowing us to strengthen enforcement and monitoring of imports and international trade."

Lion numbers in Africa have been steadily declining, from around 76,000 in 1980 to an estimated 30,000 today, with 70 percent of those living in just 10 strongholds.

"Lions are declining, and unless we do something to intervene, it's likely they will become endangered in the foreseeable future," Ashe said.

The portion of the listing banning the sale of lion parts outside the United States would help halt a trade in lion bones being sold to China, where they are being used as a substitute for tiger bones in a tonic offered as a purported health remedy, the World Wildlife Fund says.

Beginning Oct. 29, there will be a 90-day public comment period on the proposed listing of lions as threatened, and people wishing to do so can find instruction of the USFWS website.