TLANTA (AP) — Officials at Atlanta's zoo are on giant panda birth watch.

An ultrasound performed June 30 confirmed that 15-year-old giant panda Lun Lun is expecting her fourth cub. She is believed to be nearing her due date.

Beginning Wednesday, Zoo Atlanta staff has Lun Lun under 24-hour monitoring in a behind-the-scenes den. A live PandaCam video feed is running 24 hours online so panda fans around the world can watch and wait along with zoo staff.

The cub will be the first giant panda born in the U.S. this year. It will be the fourth for Lun Lun and her partner Yang Yang. All four pregnancies have resulted from artificial insemination.

___