CAIRO // Osama bin Laden threatened to kill any captured Americans if the US executes the self-professed mastermind of the September 11 attacks or any other al Qa'eda suspects. The US is still considering whether to put Khalid Sheik Mohammed and four of his fellow plotters on military tribunal for their role in the attacks. The Obama administration is also looking into recommendations for civilian trials, and is expected to announce a decision soon. In a brief 74-second audio tape aired on Al Jazeera television yesterday, bin Laden said if the US decides to execute any al Qa'eda suspects in its custody - and explicitly mentioned Khalid Sheik Mohammed - his terror network would kill American captives. He said such a decision "would mean the US has issued a death sentence against whoever of you becomes a prisoner in our hands." It was not immediately clear whether al Qa'eda currently has any US captives, but the Haqqani group - the Pakistan-based Taliban faction closest to al Qa'eda - is holding an American soldier it captured in eastern Afghanistan in June 2009. It released a video of him in December. Bin Laden said that the US president Barack Obama is following in the footsteps of his predecessor George W Bush by escalating the war in Afghanistan, being "unjust" to al Qa'eda prisoners and supporting Israel in its occupation of Palestinian land. In a veiled threat, bin Laden said Americans had previously thought their homeland was beyond the reach of his group until the September 11 attack. Khalid Sheik Mohammed, who was captured in Pakistan in 2003, is the most senior al Qa'eda operative in US custody. He is currently in detention at the US naval base at Guantanamo Bay, Cuba. In 2008, the US charged him with murder and war crimes in connection with the September 11 attacks. Pentagon officials have said they'll seek the death penalty.