Friday's debut of new pandas at the National Zoo in D.C. is the latest chapter in a long tale of "panda diplomacy" between China and the rest of the world.

After meeting with President Biden in California, President Xi Jinping signaled that he will send new pandas to the U.S., calling them "envoys of friendship between the Chinese and American peoples."

The National Zoo's three giant pandas are set to return to China in December with no public signs the 50-year-old exchange agreement struck by President Richard Nixon will continue. The departure of the bears from the nation's capital would mean the only giant pandas left in America are at the Atlanta Zoo — and that agreement expires next year.

Rusty the red panda escaped his National Zoo enclosure and was briefly free in Washington, D.C., in 2013. He has died at age 10 of unknown causes.

Zookeepers noticed something was amiss when the animals began eating less and were seen coughing and sneezing. Visitors are not at risk because the public doesn't have access to the enclosures.

Veterinarians have found what appear to be fetal tissue during an ultrasound. The zoo says she could give birth in the next couple of days.