A rare Sumatran tiger has been born at the Smithsonian's National Zoo in Washington, officials said Wednesday.

The cub was born at 4:17 p.m. Tuesday to an 8-year-old female, Damai.

"Keepers watched the birth via a closed-circuit camera and continue to closely monitor the cub, which appears to be nursing, moving and behaving normally," the zoo said in a statement.

The zoo said it is not yet sure of the cub's sex.

This is the second birth for Damai but the first via the zoo's 13-year-old male, Sparky.

"Keepers began monitoring Damai closely after she bred with Sparky in late March," the statement said.

Veterinarians confirmed the pregnancy with an ultrasound on June 8.

Sumatran tigers are critically endangered, and there may be as few as 300 to 400 still existing in the wild.

"This is such an exciting time for us, not only because we have a cub who appears to be doing great, but also because this animal's genes are extremely valuable to the North American population," Craig Saffoe, curator of the Great Cats habitat, said according to the statement.

"Now that we have had success breeding Damai this year and in 2013, it means that the keepers' patience with the introduction process, their willingness to study the cats' behaviors and learn from them and our discussions with colleagues here and at other institutions has paid off," he said.

"The result is this amazing little cub."