BOSTON — A Chinese man conspired to export devices that can be used in nuclear production to Iran for what an alleged conspirator called "a very big project and secret one," according to a federal indictment.

Sihai Cheng, also known as Alex Cheng, was brought to the United States Friday after being arrested in Britain earlier this year. He is expected to make an initial appearance in U.S. District Court in Boston on Monday.

In a 2013 indictment, Cheng is accused of conspiracy, illegal exporting of U.S. goods to Iran and smuggling.

Cheng allegedly established shell companies in China to receive pressure-measuring sensors known as "pressure transducers" from the Shanghai subsidiary of Andover, Massachusetts-based MKS Instruments Inc., according to the indictment.

The instruments can be used for various commercial applications, but they can also be used in centrifuges to convert natural uranium into a form that can be used in nuclear weapons.

Cheng is accused of conspiring with Seyed Abolfazl Shahab Jamili, of Tehran, to send hundreds of sensors made by MKS to Eyvaz Technic Manufacturing Co., a Tehran company that has supplied parts for Iran's development of nuclear weapons, the indictment states.

The U.S. Attorney's Office has previously said that MKS sent the instruments to China without knowing they were to go to Iran and is not a target of the investigation, which began in 2012.

Kathleen Burke, general counsel for MKS Instruments, said Friday that Cheng has never been an employee of MKS and the company.

"MKS is not and has never been a target of the investigation. We've provided assistance to the U.S. government during the investigation," Burke said.

The sensors cannot be exported to Iran because of the U.S. embargo.

Jamili described the types of projects for which he was procuring parts for the Iran government in emails with Cheng, according to the indictment. In a March 2007 email, "Jamili confided to Cheng that the parts he was supplying are needed in Iran for 'a very big project and secret one,'" the indictment states.

The indictment says publicly available photographs of the Natanz uranium enrichment facility in Iran show numerous MKS pressure transducers attached to Iran's gas centrifuge cascades.

It could not be determined if Cheng has retained a lawyer. Court documents filed in Boston did not list an attorney.