Al-Qaida leader Osama bin Laden has threatened to kill any captured Americans if the U.S. executes the alleged mastermind of Sept. 11.

In a new audio message aired on Al-Jazeera TV Thursday, bin Laden said if the U.S. executes Khalid Sheik Mohammed that it would mean a "death sentence" for Americans captured by al-Qaida.

Mohammed is currently in U.S. custody. The Obama administration is still debating where to hold his trial.