Six pandas bred in captivity will be released into an enclosed forest in southwestern China next year, a major step forward in the country's drive to send the endangered animals back to nature.

Yingying (L) and Gongzai, two of the six pandas to be released to a protected natural area in Dujiangyan. [China Daily]

The pandas, aged two to four, will be released into the "Panda Valley" -- 134 hectares of enclosed forest -- on Jan. 11, 2012, said Zhang Zhihe, director of the Chengdu Research Base of Giant Panda Breeding, home of the six pandas, on Wednesday at a news conference in Beijing.

Over the past 30 years, the Chengdu panda base has been trying to send captive-bred pandas back into nature, however, their efforts have seldom succeeded, as human-raised pandas have great difficulty surviving in the wild, according to a statement from the base.

Among the 10 pandas that have been released since 1983, only two are still living in the wild. Six have been sent back to the breeding center due to dramatic weight loss, one was found dead and the other is believed to have also died, it said.

Researchers believe that releasing six pandas together, unlike previous attempts to release them individually, will help them survive.

According to Zhang, after a year of observation on their health conditions and genetic backgrounds, the six -- named Xingrong, Xingya, Gongzai, Yingying, Zhizhi and Qiqi-- were carefully selected from 108 pandas living at the Chengdu base.

They will be the first group of pandas released into the "Panda Valley," which is also known as the Chengdu Giant Panda Breeding and Release Research Center and is affiliated with the Chengdu panda base.

The center, located in Majiagou in Yutang town in the city of Dujiangyan and still under construction, is designed to train giant pandas born in captivity to live in the wild.

Upon the center's completion, it will host 30 to 40 giant pandas as well as other species, including 50 to 100 red pandas, Zhang said.

Construction at the center started in May 2010 and investment is expected to reach 300 million yuan (47.6 million U.S. dollars).

China started a giant panda training project in 2003 to teach the animals to live in the wild. But the project suffered a major setback when Xiang Xiang, a five-year-old male panda, was found dead after a fight with wild pandas in a remote part of the Wolong Nature Reserve in 2007.

Xiang Xiang, who was among the ten pandas sent into the wild, was released in April 2006 after nearly three years of training.

Researchers are confident that this time the pandas will survive in the wild as the six are young and strong and their training has been improved over the years.

Chinese basketball superstar Yao Ming will attend a ceremony as an image ambassador on the day of the pandas' release, Zhang said.

Giant pandas are the world's most endangered species. About 300 giant pandas have been bred in captivity and 1,596 others live in the wild.

Zoologists believe releasing giant pandas into the wild will reduce the risk of inbreeding among the animals' wild partners.

The separation of habitats, resulting from human activities, fragmented the wild population of giant pandas, which could limit mating alternatives and lead to a high possibility of inbreeding.