Myanmar's junta has charged a US journalist detained since May with sedition and terrorism, which carry a maximum sentence of life imprisonment.

Iran PressAsia: Danny Fenster, who had been working for the local outlet Frontier Myanmar for about a year, was arrested as he was heading home to see his family in May and has been held in Yangon's Insein prison since.

The 37-year-old is on trial for reportedly encouraging dissent against the military, unlawful association, and breaching immigration law.

The additional charges under Myanmar's anti-terror and sedition laws open Fenster up to a maximum sentence of life imprisonment. The trial is scheduled to begin on November 16.

“He has become quite thin,” his lawyer Than Zaw Aung said.

Fenster was “disappointed” at being hit with the new charges, which were filed on Tuesday, his lawyer added.

The US on Wednesday urged Myanmar's junta to free Fenster immediately.

The new charges come days after former US diplomat and hostage negotiator Bill Richardson met junta chief Min Aung Hlaing in the capital Naypyidaw, handing the increasingly isolated junta some rare publicity.

Richardson said he was hopeful he had brokered a deal for a resumption of visits by the International Committee of the Red Cross to prisons — which have been filled with political inmates.

Declining to give further details, he said the US State Department had asked him not to raise Fenster's case during his visit.

Fenster last spoke with US consular officials by phone on October 31, State Department spokesman Ned Price said on Monday.

The South-East Asian country has been mired in chaos since the military ousted the elected government, with the junta trying to crush widespread democracy protests and stamp out dissent.

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