Giant pandas Mei Xiang, Tian Tian, Xiao Qi Ji depart Washington for China

Smith said it's been hard for her to accept the fact that the three giant pandas are leaving - not only in this morning, but also in the days leading up to their departure. "But ultimately our focus today is on the safe transport of these animals to China. And it's a moment of joy because this is one more step in 50 years of a successful giant panda conservation program."

She expressed the hope that such cooperation would continue for another 50 years. "Please know that the future is bright for giant pandas. We remain committed to our program and we look forward to celebrating with all of you when pandas can return to D.C.," the director said.

Xu Xueyuan, minister of the Chinese embassy in the United States who also attended the event, said that since the arrival of Meixiang and Tian Tian in Washington 23 years ago, which also marked the beginning of cooperation between China and the NZCBI, Chinese and U.S. teams "have worked closely and fruitfully on giant panda conservation and research."

Such collaboration has resulted in remarkable accomplishments on giant panda breeding, disease prevention and treatment, as well as public education, Xu said, adding that in so doing, professionals from the two countries have "contributed strongly to the mutual understanding and friendship between the Chinese and American peoples."

Noting that the NZCBI has provided "loving care" for Mei Xiang, Tian Tian and their cubs, which feature "high standard facilities" and "leading veterinary and research expertise," Xu said the pandas "have delighted millions of visitors in the U.S. and from other parts of the world. "

"Today, agreed by both sides, it is time for Mei Xiang and Tian Tian to bring Xiao Qi Ji back home," Xu continued, adding that the three pandas are in good health and ready for the flight.