WASHINGTON (AFP) - Urging Americans to curb trophy killings and not be "cowardly lions," US lawmakers introduced legislation Friday that would prevent the kinds of controversial hunting that brought down Zimbabwe's beloved beast Cecil.

Senate Democrat Robert Menendez's bill would expand the import-export restrictions of the 1973 Endangered Species Act to include animals that are not just listed as endangered or threatened, but those that are "proposed to be listed" as such.

The US Fish and Wildlife Service, which maintains the US endangered species list, last October proposed to list the African lion as threatened due to habitat loss and increased human-lion conflicts.

It has yet to finalise any lion protections.

The two-page Conserving Ecosystems by Ceasing the Importation of Large (CECIL) Animal Trophies Act is named after a lion killed by a US dentist in a hunt that triggered global anger.

Cecil was considered an iconic attraction for tourists at Zimbabwe's Hwange National Park.

The hunter, Walter Palmer, used a bow and arrow to shoot Cecil, who was tracked for a second day before being shot dead.

"Let's not be cowardly lions when it comes to trophy killings," Menendez said, calling Cecil's demise "senseless."

"Cecil's death was a preventable tragedy that highlights the need to extend the protections of the Endangered Species Act. When we have enough concern about the future of a species to propose it for listing, we should not be killing it for sport."

Three other Democrats have sponsored the legislation.

It is unclear whether Republican lawmakers - who often describe themselves as hunters and support gun rights for hunters - will back the bill.