China is expected to agree to donate a pair of endangered crested ibises to Japan during a summit this week to mark the steady improvement of bilateral ties, diplomatic sources said Sunday.

If the donation is agreed on by Prime Minister Shinzo Abe and Chinese Premier Li Keqiang on Wednesday in Tokyo, it will be the first by China in 11 years.

The move is aimed at helping repopulate the species, which went extinct in Japan in 2003. Recently, inbreeding has raised fears that Japan's slowly recovering ibis population is developing compromised immune systems.

"In order to secure genetic diversity, we have asked for the donation of new ibises from China," Chief Cabinet Secretary Yoshihide Suga said at a news conference Monday.

The birds are expected to be delivered to Sado Island, Niigata Prefecture, which hosts an ibis conservatory.

In 1999, two Chinese crested ibises were brought to Sado after then-Chinese President Jiang Zemin pledged to present specimens to Japan. Three more were sent to Japan by 2007.

In 2011, then-Chinese Premier Wen Jiabao expressed his intention to donate ibises to Japan, but the plan was shelved after a territorial row erupted over Japan's effective nationalization of the Senkaku Islands, which China claims as Diaoyu and Taiwan as Tiaoyutai.

Ibises are designated a special natural treasure in Japan, but Japanese-born ibises were hunted to extinction in 2003, forcing it to artificially breed and train them for reintroduction into the wild.

At present, more than 280 ibises are estimated to be living in the wild in Japan.