BEIJING, Aug 4 (AP) -- China will fly a pair of giant pandas to Spain next month, state media reported Saturday, following through on a goodwill gesture promised during a visit by Spanish King Juan Carlos to Beijing earlier this year.

The pair, seven-year old "Bing Xing" and four-year old "Hua Zui Ba" will be flown from their home in the southwestern city of Chengdu to Madrid on Sept. 8 by chartered plane for a 10 year stay, the Xinhua News Agency said.

The pair are due to go on display two weeks after their arrival, Xinhua said. The loan had been agreed to in June during the King's visit.

The giant panda is unique to China and serves as a sort of unofficial national mascot, imbuing such loans with particular political overtones. China regularly sends the animals abroad as a sign of warm diplomatic relations or to mark breakthroughs in ties.

Financial details of the arrangement with Spain were not revealed, but China uses payments from zoos that host lent pandas to fund extensive research and breeding programs. Under such loan agreements, any panda cubs born overseas to lent animals also remain the property of China.

The panda is one of the world's rarest animals, with about 1,590 living in the wild in China, mostly in the western provinces of Sichuan and the Shaanxi. Another 180 have been bred in captivity.

Female pandas normally become sexually mature between 4 and 5 years old. They can get pregnant once a year and usually give birth to one or two cubs at a time. More than 20 pandas were born in captivity in China last year.