WASHINGTON (AP) — Three decades after the U.S. started destroying its chemical weapons, it still has more than 3,000 tons. That's about three times what Syrian President Bashar Assad is believed to possess.
The remaining U.S. arsenal weighs about as much as three dozen Boeing 737s loaded for takeoff.

While the U.S. has eradicated 90 percent of its original arsenal, the process won't be finished until 2023.

Deadlines have come and gone, and been extended. Like other nations, the U.S. has found complying with the Chemical Weapons Convention is easier said than done.

As the U.S. pushes Syria to surrender its chemical weapons arsenal, the challenges that have hindered America's efforts for a generation illustrate the overwhelming task of securing and dismantling Assad's stockpiles in the middle of a civil war.