China has extended a diplomacy agreement with the US allowing two pandas (12-year-old Mei Xiang and 13-year-old Tian Tian) an extension to their stay at the Washington National Zoo for another five years.

Since 2000, the cooperative agreement between the two countries has loaned a panda pair to the US for the last ten years.

The deal, signed by the Smithsonian National Zoo and China Wildlife Conversation Association, calls for scientists and breeding experts to visit the pandas and highlight the significance of their breeding and conservation programme.

Director of the Simthsonian National Zoo Dennis Kelly, said "This new agreement solidifies our mutual interest, our commitment and friendship, it's one of the best examples about how like minded people who are interested in conservation. We can work to achieve great conservation. We are the nation's zoo. As part of the Smithsonian we belong to the American people. Here, all families, all people can visit and learn about these magnigicent ambassadors."

Pandas are difficult to breed because females ovulate only once a year and can only become pregnant during the two or three-day period.