US circuses are circling the wagons against a proposed law in Congress that would ban using elephants under the big top, a tradition that animal rights activists say causes terrible suffering.

The bill, introduced this month in the House of Representatives by Virginia Congressman Jim Moran, aims directly at traveling circuses by seeking to outlaw exotic or wild animals from performances if they have been traveling within the previous 15 days.

That would mean an end to the days of elephants balancing on stools, tigers and lions jumping through fiery hoops, monkeys on wheels, or other popular staples of the ring.

"It is clear that traveling circuses cannot provide the proper living conditions for these exotic animals," Moran said in a statement.

He noted that zoos, aquariums, horse races and permanently housed animals used for shooting movies and other filming events would not fall under the ban.

The law is the first attempt for a decade to put an end to the iconic circus routines, which animal rights activists say are based on cruel training methods and harsh, unsafe living facilities.

America's most famous big top outfit, Ringling Bros and Barnum & Bailey, sent out an email appeal to supporters this week, saying "the Greatest Show on Earth" needed help "to make sure this family tradition continues."

Stephen Payne, a spokesman, said the bill was not pro-animal, but simply against circuses.

"It's to do with putting Ringling Brothers and other circuses out of business," Payne told AFP.

"This is just anti-circus legislation that's really not necessary because we're already inspected and regulated under federal laws, state laws and local laws in almost every state we play."

Payne said animal rights groups did not understand the circus business and were out of touch with Americans.

"They are at the fringe: they don't want animals for entertaining, they don't want them for food, they don't want them for pets," he said.

"What we get are millions and millions of families coming to see Ringling Brothers and Barnum and Bailey."

According to Ringling Brothers, their circuses not only treat elephants well, but help preserve the Asian elephant breed, thanks to a self-sustaining, 50-strong herd that has seen 23 births since 1995.

The company also funds elephant conservation programs in the United States and in countries such as Sri Lanka.

"Asian elephants have been part of Ringling Brothers for 141 years," Payne said. "P.T. Barnum once brought his elephants across the Brooklyn Bridge to convince New Yorkers it was structurally sound."

But Ed Stewart, from the Performing Animal Welfare Society, or PAWS, said Ringling's elephants are not nearly as happy as their gaudy outfits and circus tricks are meant to suggest.

"There is no state of the art keeping animals in captivity. The state of the art is Zimbabwe and India and the wild, the hills of Virginia, but not in cages," he said at a press conference after the bill was introduced.

Stewart said children should stop being shown circus animals altogether.

"Real educators have to overcome what children see in the circus. It would be better if they didn't even have an experience with an elephant or a tiger or a lion if that's the experience," he said.