NEW YORK (REUTERS) - A Chinese national and former L-3 Communications Holdings Inc engineer was sentenced to nearly six years in prison following his conviction for illegally exporting details of sensitive US military technology to China.

Sixing Liu, 49, had been convicted in September by a federal jury in Newark, New Jersey, on nine of 11 counts, including possession of stolen trade secrets, violating the Arms Export Control Act and lying to federal agents.

Prosecutors said the defendant, who is also known as Steve Liu, stole thousands of computer files that detailed the performance and design of guidance systems for missiles, rockets and unmanned drones.

Liu then made several presentations at Chinese universities and government-organised conferences about the technology without L-3's permission, hoping it would eventually help him get a job in China, prosecutors said.

"Instead of the accolades he sought from China, Sixing Liu today received the appropriate reward for his threat to our national security: 70 months in prison," Mr Paul Fishman, the US Attorney in New Jersey, said in a statement.

The sentence was imposed on Monday by US District Judge Stanley Chesler in Newark, with restitution to be determined later.

Liu has been in custody since the verdict. Prosecutors said he was a risk to flee.

Mr James Tunick, a lawyer for Liu, said in a phone interview he plans to appeal the conviction and sentence.

"Dr Liu made a mistake by having these files on his computer, but we have always maintained that it didn't rise to the level of a criminal act," Mr Tunick said. "He surely did not intend to harm the interests of the United States."

Mr Tunick said Liu's sentence was in the middle of the 63- to 78-month term recommended under federal sentencing guidelines.

He said he had requested a prison sentence of one year and one day for his client, including the six months already spent in custody.

Liu had worked in L-3's space and navigation unit in Budd Lake, New Jersey, from March 2009 until November 2010.

Prosecutors said federal agents found Liu at Newark Liberty International Airport on Nov 29, 2010, as he returned from a trip to Shanghai, in possession of a private computer containing the stolen material.

L-3 was not a defendant in the case, and has said it cooperated with authorities.