Mei Xiang the panda Photo: AFP

A rare giant panda called Mei Xiang gave birth to a cub at the Smithsonian National Zoo in Washington on Saturday, winning praise from delighted zoo officials for being an "excellent mother" after she picked her tiny offspring up.

The tiny cub - pink, hairless and only about the size of an adult mouse - was born at 5:35 pm (2134 GMT), the zoo said in a statement, and Mei Xiang reacted by picking up the cub.

"All of us are thrilled that Mei Xiang has given birth. The cub is vulnerable at this tiny size but we know Mei is an excellent mother," zoo director Dennis Kelly said.

The mother panda's care team began preparing for the birth after they saw Mei Xiang's water break about an hour earlier. They hope to carry out a neonatal exam in the coming days and won't know the cub's sex until a later date. 

The new mother was artificially inseminated in April with frozen semen from a male giant panda named Hui Hui that resides at the China Conservation and Research Center for the Giant Panda in Sichuan Province.

She was also inseminated with fresh semen from the zoo's male giant panda Tian Tian. DNA tests will establish which is the father.

Pandas are famously challenging to breed in captivity. Mei Xiang had a cub in 2005 which was sent to China, and another Bao Bao. It is two years old and lives with her.

But she also lost at least two other cubs, one that was stillborn in 2013 and another that lived just six days in 2012.

This year, Mei Xiang exhibited signs of pregnancy in July that included sleeping more, eating less, building a nest and spending more time in her den.