Two giant pandas on Tuesday departed the mainland for a zoo in the US capital.

Bao Li, a male panda, and female Qing Bao, both three years old, were headed to the Smithsonian National Zoo in Washington under a decade-long breeding and research agreement.

"China and the United States have made orderly arrangements... to ensure that the two giant pandas will arrive at the Washington National Zoo safely and smoothly," the China Wildlife Conservation Association said in a statement.

Lu Yongbin, party secretary of the China Conservation and Research Center for the Giant Panda committee, said at the farewell ceremony in Sichuan that the new round of China-US cooperation will boost bilateral collaboration in endangered species and biodiversity protection and enhance the friendship between the Chinese and American people.

Bao Li and Qing Bao were accompanied by an experienced breeder and a veterinarian to help them adapt quickly to their new environment.

Only a few of the beloved black-and-white bears remain in the US after almost all were returned to China in recent years under pre-arranged contracts – including all three of the National Zoo's pandas last November.

President Xi Jinping said after meeting his counterpart Joe Biden at a summit in California last November that China could send new pandas as "envoys of friendship between the Chinese and American people".

In August, San Diego Zoo welcomed two new giant pandas, the first to be sent by the nation to the US in 21 years.

Anticipation for the pandas' arrival in Washington was high, with the National Zoo's website emblazoned with a banner that read: "The pandas are coming."

Something "giant" is "coming to Washington", the zoo said in a post on X, adding that it would be closed on Tuesday but that for "the safety of the pandas and staff, we will not disclose any additional timing".

Preparations were well underway at the zoo, where pandas have been star attractions for decades. Renovations have been undertaken at the panda habitat "to enhance the safety of the facilities and maximise space for the bears to roam", according to the zoo's website.

The new structures constructed for the pandas include shallow pools to allow them to bathe and bamboo stands that require the bears to mimic the foraging techniques they would use in the wild.

The bears will not, however, be available to the public for more than a month after their arrival, as they will need to be quarantined and to acclimate to their new habitat.

While en route, the pandas' in-flight meals will include bamboo shoots, carrots and Chinese cornbread, the China Wildlife Conservation Association said. (AFP/Xinhua)