A giant panda lent to the United States by China and living at the National Zoo in the US capital has given birth to a cub, zoo officials said Monday. The birth occurred at about 10:46 pm local time Sunday (0246 GMT Monday), according to the zoo\'s chief veterinarian, Suzan Murray. Mei Xiang, as the mom panda is called, \"is cradling her cub closely, and she looks so tired,\" Murray said in a statement. \"But every time she tries to lay down, the cub squawks, and she sits right up and cradles the cub more closely,\" Murray added. \"She is the poster child for a perfect panda mom.\" Zoo officials said they believed there was only one cub, but they would know for sure later in the day if the cub was to have a twin. They said their goal was for Mei Xiang to raise this cub naturally. In the meantime, the cub and its mom are being monitored by webcam