The retrial of a Delaware man who confessed to drunkenly snapping the finger off an ancient Chinese terra-cotta warrior statue at the Franklin Institute in 2017 has been indefinitely postponed due to the coronavirus outbreak in the relic’s native country and U.S. efforts to stop the illness from spreading here.

In a court filing Wednesday, federal prosecutors said several Chinese witnesses essential to their case against Michael Rohana, 26, would be unable to travel to Philadelphia for the retrial that had been scheduled to start Feb. 18.

Their arrival has been barred under the travel ban the Trump administration instituted on all foreign nationals who have visited China in the last two weeks. U.S. officials have not indicated when it might be lifted.

At Rohana’s first trial in April, several officials from China’s Shaanxi province testified about the history and value of the more than 2,000-year-old statue, one of hundreds discovered during excavations of the tomb of China’s first emperor, Qin Shi Huang, that began in the 1970s.

The Chinese government strictly regulates research and restoration of the statues, considered national treasures. It has prohibited their purchase or sale. The Franklin Institute was one of two U.S. museums Chinese officials allowed to host a traveling exhibit of relics in 2017.

Rohana never disputed he broke the thumb off the statue during an after-hours “ugly sweater” Christmas party the institute hosted that year. But his trial ended in a hung jury and mistrial after defense lawyers questioned whether he’d been appropriately charged under a law typically used to prosecute art thieves.