WASHINGTON -- The father of a U.S. soldier who was taken prisoner in Afghanistan thanked the motorcycle riders of Rolling Thunder on Sunday for raising awareness of missing-in-action troops and prisoners of war.

At the annual Rolling Thunder rally on the National Mall, Bob Bergdahl promised his son: "You will come home. We will not leave you behind."

Army Sgt. Bowe Bergdahl, 26, of Hailey, Idaho, was taken prisoner in Afghanistan nearly three years ago. He is the subject of a proposed prisoner swap in which the Obama administration would allow the transfer of five Taliban prisoners long held at the U.S. military prison at Guantanamo Bay, Cuba.

Bergdahl said he couldn't be happier with the government's efforts to return his son.

"This is a complicated issue and it's going to demand all aspects of American government. And we need joint cooperation, we need every level, every agency and every dimension of American government to cooperate and pay attention," he said. "We're on a mission to get our son home and we're not going to stop until we accomplish that."

Motorcyclists attending the ceremony wore yellow wristbands with Bergdahl's name and the date he went missing on them. Many also wore the traditional biker gear of leather vests and riding boots, even though temperatures reached the 90s.

Hundreds of thousands of bikers, including military veterans and non-veterans, gathered in the nation's capital this weekend for the Rolling Thunder rally.

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  • Rolling Thunder 2012

  • Rolling Thunder 2012

    Bob Bergdahl, father of Army Sgt. Bowe Bergdahl of Hailey, Idaho, who is being held captive in Afghanistan, shakes the hand of Gerald McCullar of Washington, Ill., who is portraying a prisoner of war, after he speaks at the the annual Rolling Thunder rally for POW/MIA awareness, in D.C., Sunday, May 27, 2012.

  • Rolling Thunder 2012

    Audience members bow their heads in prayer during the annual Rolling Thunder event on the National Mall ahead of Memorial Day in D.C., Sunday, May 27, 2012.

  • Rolling Thunder 2012

    Bob Bergdahl, father of Army Sgt. Bowe Bergdahl of Hailey, Idaho, who is being held captive in Afghanistan, speaks at the the annual Rolling Thunder rally for POW/MIA awareness, in D.C., Sunday, May 27, 2012. (AP Photo/Charles Dharapak)

  • Rolling Thunder 2012

    Motorcycles drive from the Memorial Bridge during the annual Rolling Thunder parade ahead of Memorial Day in D.C., Sunday, May 27, 2012.

  • Rolling Thunder 2012

    People watch as motorcyclists ride down Constitution Avenue during Rolling Thunder May 27, 2012 in D.C.

  • Rolling Thunder 2012

    People watch as motorcyclists ride down Constitution Avenue during Rolling Thunder May 27, 2012 in D.C.

  • Rolling Thunder 2012

    Motorcyclists ride down Constitution Avenue during the Rolling Thunder 2012 May 27, 2012 in D.C.

  • Rolling Thunder 2012

    Donna Street holds up inflatable soldiers while watching Rolling Thunder ride into the city May 27, 2012 in D.C.

  • Rolling Thunder 2012

    A motorcyclist rides past the National Archives during the Rolling Thunder 2012 May 27, 2012 in D.C.