Hsing-Hsing, the only giant panda in the US National Zoo, died here Sunday, a zoo official announced.

Hsing-Hsing was put to sleep at around 7 a.m. by injection after suffering from kidney disease for 6 months, said Bob Hoage, chief of the zoo's public relations department.

The panda was becoming increasingly weak and inactive in recent days and zoo officials determined that it was impossible for him to maintain his quality of life, he said.

"His system has failed and his eyesight has got very weak for the last week, the keeper feels very sad, so it is best to put him to sleep," Bob said.

"I'm very sad to announce the news, he has been loved by millions of visitors," Bob added.

"His death is like the passing of a close friend," said National Zoo director Michael Robinson.

The panda was 28, an advanced age for the rare animal. Hsing- Hsing was discovered to have non-reversible kidney disease last May.

Hsing-Hsing's death leaves only five giant pandas in American zoos, three in San Diego and two that arrived earlier this month in Atlanta.

Hsing-Hsing and his mate Ling-Ling came to the National Zoo from Beijing in 1972, a gift from the Chinese government following President Nixon's visit to China that year.

The two produced five offspring, but none lived longer than four days. Ling-Ling died of heart failure in 1992 at age 23.

Bob said the zoo is still in negotiation with the Chinese authorities to get a pair of new giant pandas from China.

"We have very good facilities for giant pandas in the zoo," Bob said. (Xinhua)