Updated

The US commander in Afghanistan said Sunday he hoped that an American soldier held by the Taliban would soon return home safely as troops marked the fourth anniversary of his disappearance.

US Army Sergeant Bowe Bergdahl vanished on June 30 2009. He is the only known American soldier held by the Taliban, who have released several videos showing him to be alive.

"Four years later, we are still waiting for Sergeant Bergdahl's safe return and it is my sincere hope that the wait will soon come to an end," said US General Joseph Dunford, commander of NATO troops in Afghanistan.

"To Sergeant Bergdahl's family, I want to say that we know you have not given up hope and neither have we," the general said.

The Taliban on June 18 opened an office in the Gulf state of Qatar, reviving hopes in the United States that contacts might resume on a prisoner exchange that would bring Bergdahl home.

Efforts to negotiate an exchange between Bergdahl and five Taliban prisoners in Guantanamo Bay collapsed last year.

The US State Department says his release is a priority.

Bergdahl has said in a video that he was captured when he fell behind his unit during a patrol.