The Terracotta Army is one of China's most important archaeological findings.
Chinese authorities have demanded "severe punishment" for a man who allegedly stole the thumb of the precious statue loaned for display at the Philadelphia museum, Chinese state media reported.
The 2,000-year-old statue, worth some USD 4.5 million, is one of 10 on loan to the Franklin Institute in Philadelphia. The exhibit will run until March 4.
The statue, which is a cavalryman, dates back to at least 209 BC.
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The related US departments should be held responsible for the damage, and guarantee the safety of the relics on display, state-run Xinhua news agency quoted the department as saying.
The department has sent a notice to the museum informing its decision to dispatch two experts to repair the Terracotta warrior statue, it said.
The Shaanxi Cultural Heritage Promotion Centre has organised over 260 overseas exhibitions over the past 40 years, and has never come across a situation such as this, an official with the centre was quoted in the report as saying.
They were built in 210 BC by Chinese emperor Qin Shi Huang who believed they would protect him in the afterlife.
The statues were discovered in China's Xi'an city in 1974 by a group of Chinese farmers. The Terracotta Museum in Xian attracts thousands of tourists from home and abroad.
Last week, Michael Rohana, 24, was arrested for stealing the thumb which he reportedly broke while he was attempting to take a selfie. He was later released on bail.
Rohana used a mobile phone as a flashlight and took a selfie with one of the warriors, China's state-run Xinhua news agency quoted the FBI as saying.
A spokeswoman for the Philadelphia museum said that the statue will be repaired, adding that a security contractor did not follow standard procedures at the night of the alleged theft.