(Reuters) - A Chinese citizen pleaded guilty on Friday to charges of trying to illegally export to China high-grade carbon fiber used primarily in aerospace and military applications, the U.S. Justice Department said in a statement.

Fuyi Sun, 53, who pleaded guilty before U.S. District Judge Alvin Hellerstein in New York federal court, admitted he tried to procure the carbon fiber for the Chinese military, the statement said. He faces a maximum sentence of 20 years in prison when sentenced on July 26, it said.

A lawyer for Sun could not immediately be reached for comment.

Sun was arrested last April after he traveled to obtain M60 carbon fiber, which is used in military drone aircraft, from people working as undercover U.S. law enforcement agents, prosecutors said.

Sun began trying to acquire the carbon fiber around 2011, prosecutors said. He repeatedly told the agents the fiber he wanted would go to the Chinese military, with which he said he had a close relationship, according to charges filed against him.

Prosecutors say Sun asked the undercover agents about buying about 450 kilograms of carbon fiber for more than $62,000. When he met the agents in New York last April, they say, Sun agreed to pay $25,000 for carbon fiber.

He took steps to conceal the purchase from U.S. authorities, including asking the undercover agents to use “banana” as a code word for “carbon fiber” and falsifying customs documents.

His arrest underlined tensions between the United States and China over intellectual property rights. The FBI has said cases of economic espionage rose 53 percent in 2015, the majority of which involved Chinese nationals.