MIAMI - The U.S. government has asked a judge to dismiss a lawsuit that seeks to overturn a nationwide ban on four giant snake species.

Attorneys for Interior Secretary Sally Jewell and the U.S. Fish and Wildlife Service say the United States Association of Reptile Keepers has not sufficiently explained why importing the snakes into the U.S. or transporting them across state lines was vital to research and conservation activities among its members.

In a motion Friday in federal court in Washington, D.C., the government dismissed the association's claims that snake sales funded those activities.

"Not only are these interests entirely economic, they are also totally unrelated to the environment: they involve the breeding and selling of captive snakes as part of the pet industry," the motion states.

The North Carolina-based association says the ban has cost reptile breeders, handlers, hobbyists and vendors tens of millions of dollars. In December, the group challenged the science behind the ban in a lawsuit.

The government's attorneys also said the lawsuit failed to support claims about economic losses felt by the association or its members.

"We still feel very confident about our position," Joan Galvin, an attorney representing the reptile keepers association, said Tuesday.

The ban on Burmese pythons, yellow anacondas and northern and southern African rock pythons was announced in 2012. Wildlife officials say it protects native wildlife and will help prevent non-native snakes from spreading, as Burmese pythons have in Florida's Everglades.

Florida's population of Burmese pythons, which are native to India and other parts of Asia, likely developed from pets let loose either intentionally or in the aftermath of Hurricane Andrew in 1992.

A bipartisan group of 18 lawmakers recently asked the Obama administration to extend the current ban to five other types of giant snakes: boa constrictors, reticulated pythons and three species of anacondas. They said the snakes pose an "unacceptable and preventable risk" to human safety and native ecosystems.