The Toronto Zoo says it has reached an impasse with a California animal sanctuary over the planned move of three of its elephants.

The zoo says it is trying to fulfil legal requirements in order to safely relocate the elephants.

But it says the PAWS facility has failed to provide medical records for its own elephants, despite repeated requests.

Toronto Zoo CEO John Tracogna says it would be irresponsible to move the elephants to another home without proof of its operations and medical history.

Toronto city council voted in late October to send the three elephants to the U.S. facility after groups voiced concern about the animals' welfare.

Animal activist Bob Barker had offered to fund a $880,000 plane flight but has recently threatened to back off from his commitment.

Earlier this month, the zoo was denied accreditation by the Association of Zoos and Aquariums for the first time in 30 years, partly due to the decision to move Iringa, Toka and Thika to the PAWS sanctuary.

The association, a group of experts in animal management and care, evaluates zoos on a series of standards, including veterinary care, education programs, safety and governance.

Tracogna has said the key issue in that decision was governance and had nothing to do with its care of animals.

The zoo will continue to request the health information from PAWS, Tracogna said in a statement Monday.

"We acknowledge that the PAWS facility has many redeeming qualities and we are fully prepared to move the elephants under conditions that ensure the health of the elephants involved," he said.