Three Chinese archeologists left Xi'an, capital of northwest China's Shaanxi Province, Friday for the United States to help with the restoration of two Chinese Tang Dynasty (618 AD - 907 AD) relics housed at the University of Pennsylvania.

The university asked the Shaanxi-based Daming Palace Foundation, affiliated with the cultural relics bureau, to recruit experts to help with restoration of the relics,two horse sculpture reliefs, which were smuggled to America in 1914, said a foundation spokesman.

The relics were among six stone horse carvings discovered in the Mausoleum of Emperor Li Shimin (or Taizong of the Tang Dynasty) in Shaanxi. The other four are housed in the Museum of Ancient Steles in the capital of Shaanxi.

The spokesman said the three Chinese experts would give much needed advice on the restoration of the relics.

"The two horse reliefs over thousands of years have decayed and been damaged by humans. They were even once cut into several pieces by tomb robbers for transport," said Zhou Ping, one of the three experts.

She said it was no easy job to restore the relics.

The six horse reliefs once lined the corridor of the emperor's mausoleum. According to historical documents, the carvings were modeled on the emperor's favorite horses.