The offer, relayed by a Mauritanian news site, comes from Moktar Belmoktar, head of an al Qaeda splinter group. He demands that the United States free Egyptian Omar Abdel-Rahman, the Blind Sheikh, convicted of masterminding the 1993 World Trade Center bombing and Pakistani-American neuroscientist Aafia Siddiqui, who was jailed for 86 yearsfor trying to kill US troops and FBI agents in Afghanistan four years ago. In return two American hostages claimed to be held at the Algerian In Amenas gas field will be freed.