Giant panda Fu Ni and her partner Wang Wang have failed to mate for a fifth year, Zoos SA says.

Fu Ni could have been pregnant and reabsorbed the foetus or she may have experienced a phantom pregnancy after being artificially inseminated last year.

The only way to confirm a panda pregnancy is with an ultrasound but Fu Ni would not co-operate for the procedure.

“We have every hope that she will go on to become a mother in the future,” Zoos SA chief executive Elaine Bensted said.

Female pandas have a very short fertility window of 48 hours, which is why breeding can be so difficult.

But partner Wang Wang’s sperm quality has improved significantly, which the zoo says is a promising sign for years to come.

AAP