The US has asked Australia to extradite a former marine accused of breaking American arms control laws by training Chinese fighter pilots.

The United States government has sent an extradition request to Australia for former US Marine pilot Daniel Duggan, who is accused of breaking US arms control law by training Chinese military pilots to land on aircraft carriers.

Daniel Duggan, a former US citizen, has been in custody since his arrest in Australia in October.

Mr Duggan says he hasn't broken any laws and his lawyer argues the charges are politically motivated.

Duggan is accused of providing “military training” to Chinese pilots at a “test flying academy” in South Africa more than a decade ago. The former U.S. marine pilot, an Australian citizen who has renounced his U.S. citizenship, was arrested two months ago in the New South Wales city of Orange, west of Sydney, at the request of the U.S. government.

The United States has now made a formal request for his extradition. Duggan has denied breaking any U.S., Australian or international laws. His lawyer, Dennis Miralis, said it would be a miscarriage of justice if he was sent to face a trial in the United States.

Miralis told reporters outside the court in Sydney Friday that Duggan was being mistreated in custody.

“We are also filing with the United Nations Human Rights Commission a complaint about Mr. Duggan’s on-going inhumane treatment in custody, including a lack of explanation as to why he continues to be refused medical treatment," said Miralis. "In addition to that we are also concerned that up until now Mr Duggan’s overall treatment has fallen well below the standards expected of Australia under international law.”

Duggan’s arrest coincided with warnings from Australian and British authorities over former air force personnel being offered lucrative contracts to train pilots in China.

Australian Defense Minister Richard Marles announced last month an inquiry into former military veterans being recruited by China.

Marles warned that anyone compromising Australian military or state secrets would be committing “a very serious crime.”

Duggan’s extradition hearing in Sydney has been adjourned until Dec 20.