(Updates with Crisis Group statement) By Sahal Abdulle MOGADISHU, Nov 27 (Reuters) - Somali Islamists on Monday dismissed as fake two letters purportedly signed by their most influential leader and which led to a U.S. warning of possible suicide attacks in Kenya and Ethiopia. Washington issued its warning to U.S. citizens on Nov 2 in response to what it said were "terrorist threats emanating from extremist elements within Somalia". The Kenyan Sunday Nation newspaper reported it had obtained two letters said to be signed by Islamist leader Sheikh Hassan Dahir Aweys, who appears on U.S. and U.N. terrorism lists, but could not establish their authenticity. It said the letters called for the assassination of 17 prominent Kenyans and Somalis, an uprising by ethnic groups in Kenya and Ethiopia and for militia fighters of the Islamists' feared Shabab arm to mass on the Kenya-Somali border. A U.S. embassy spokeswoman said on Sunday the letters made specific threats against public targets in Ethiopia and Kenya, called for suicide attacks, and led to Washington's warning. "An assassin will not write a letter and say I will carry out a plan. Even in the copy we saw, they could not get the letterhead right," Ibrahim Hassan Addow, in charge of foreign affairs for the Islamists, told Reuters. "Those who want attack us and bring foreign troops to Somalia want to use this cheap tactic to get American support ... It is unfortunate that a State Department official accepted this and used it in American foreign policy towards Somalia." The letters surfaced amid belligerent rhetoric and heightened fears that a standoff between Somalia's interim government and rival Islamists may spiral into a regional war, sucking in neighbouring countries. U.S. embassies in Kenya and Tanzania were the target of truck bombs in 1998 that killed more than 200 people. Kenya has previously expressed concern that one of the alleged masterminds was sighted in Mogadishu and may be operating inside Kenya. The U.S. warning came two weeks after Somali President Abdullahi Yusuf addressed diplomats, citing a document, described as an order by Aweys approving both his and Prime Minister Ali Mohamed Gedi's assassination. Diplomats say the letters were passed around by members of the Ethiopian-backed interim government, which has been seeking foreign peacekeepers since October 2004. Many diplomats doubt their authenticity and say they are part of a push to get U.S. backing for a waiver to a 1992 arms embargo on Somalia, to permit peacekeepers to enter the country legally with their weapons. On Monday, the International Crisis Group think tank urged the U.N. Security Council not to side with the government by agreeing the waiver, and instead to urge both sides to resume peace talks without preconditions. "As so often in Somalia, the consequences of an ill-considered intervention are likely to be more conflict, not less," Crisis Group said. "Military measures must remain a weapon of last resort."
