Actress and animal rights activist Olivia Munn has fired off a letter to the US Secretary of Agriculture in a bid to save an ageing elephant from participating in controversial circus rides.

The Newsroom star has teamed up with campaigners at the People for the Ethical Treatment of Animals (PETA) to call for Nosey's release from exhibitor Hugo Liebel, who has reportedly been forcing the big mammal to continue working at fairs and circuses despite showing signs it is suffering from arthritis.

Munn wants top politician Tom Vilsack to order representatives from the US Department of Agriculture (USDA) to step in and place Nosey in a sanctuary under the Animal Welfare Act, and permanently revoke Liebel's exhibitor's licence for the alleged mistreatment of the animal.

In the open letter, the actress writes in part, "As an elephant lover, I'm troubled that the USDA is allowing this abuse to continue and has failed to ensure that this lame elephant is never forced to perform again.

"Elephants were never meant to be locked inside cramped trailers, kept in chains, or forced to walk in endless circles carrying riders on their backs. This has been Nosey's life, and it has taken a toll on her body. Elephants live about as long as we do, but at just 32 years old, Nosey is showing signs of crippling arthritis, which is one of the main reasons why captive elephants are euthanized.

"The USDA has the power to make sure that this condition is not a death sentence for Nosey. If she is placed in a reputable sanctuary, where she would have acres of soft earth on which to roam free, pools to wade in to ease the pain in her joints, and access to expert veterinary care, Nosey could have many happy years ahead...

"The USDA's own records show that Nosey has been exploited, mistreated, and neglected her entire life. It's time to step up and do the right thing for this animal by revoking Liebel's license, seizing Nosey, and sending her to a sanctuary. Her life depends on it."