The brother of jailed Washington Post correspondent Jason Rezaian has appealed to a U.N. human rights panel to urge his release from detention in Iran.

Ali Rezaian made the plea Tuesday at a working group on arbitrary detention at the Human Rights Council meeting in Geneva.

His voice trembling, he said his brother was held for months in solitary confinement, had lost 25 kilograms (about 50 pounds) and suffered untreated infections, respiratory troubles and deteriorating mental health. He called his brother's detention "illegal and inhumane."

Jason Rezaian was arrested in July 2014 and is awaiting a verdict in his closed-door espionage trial. The case has been widely criticized by the U.S., press freedom organizations and the Post. He reportedly faces up to 10 to 20 years in prison if convicted.