MIAMI (AFP) - Ringling Brothers, America's best-known circus, announced Monday it will relocate all of its elephants to a conservation centre in Florida by May, advancing the retirement date for the giant pachyderms by more than a year.

"Feld Entertainment announced today that all of the Asian elephants from their travelling circus units will be moved to their permanent home at the Ringling Brothers Centre for Elephant Conservation in Florida in May 2016," the parent company for the circus said in a statement.

"There they will join the rest of the Ringling Brothers' herd of Asian elephants, for a total of 42 at the conservation centre."

The 145-year old "Greatest Show on Earth" - bowing to criticism from animal rights groups - announced in March that it would phase out use of their emblematic elephants, long a centerpiece of their annual travelling show.

Feld Entertainment originally had said the elephants would be gradually withdrawn from the big top and completely gone only by 2018, but it now has accelerated that retirement date.

However, some animal rights advocates, including People for the Ethical Treatment of Animals (PETA) said sending the animals to the Ringling's conservation centre is a far from satisfactory outcome.

"It's not all sunshine and roses for the 'retired' elephants," PETA said in a statement.

"At Ringling's grandiosely named Centre for Elephant Conservation elephants will no doubt still be chained on a daily basis, be forced to breed, be deprived of opportunities to interact and socialise normally, and continue to live in fear of being hit with bullhooks," the statement said.

It urged Ringling to send the elephants to a bona fide animal sanctuary with conditions similar to those they would find in their natural habitat.

"Pulling elephants from the road is a step in the right direction, but... the elephants should be taken to legitimate sanctuaries, and all the animal acts should come to an end." Ringling Brothers in 2011 had to pay a US$270,000 (S$388,000) fine after receiving citations over how it treated its animals, among other infractions over the years.

An increasing number of US towns and cities have adopted anti-elephant ordinances forbidding circus acts with elephants to enter the municipal limits.

The circus said it would continue to feature other animals in its acts, including tigers, lions, horses, dogs and camels.