SRI LANKA's Tamil Tigers will go underground rather than “fight to the last man” once a northern offensive that has cut their strength to 3,000 fighters from 12,000 nears its end, Sri Lanka's army chief said on Thursday. Lieutenant-General Sarath Fonseka also said he had no clear time frame for retaking territory held by the Liberation Tigers of Tamil Eelam (LTTE), because his aim was killing all of the insurgents rather than seizing ground. “We don't want to end up in a situation like in Iraq when you're moving fast, but you left behind a whole army who will resort to guerrilla tactics,” Fonseka told Reuters in an interview at Army Headquarters in the capital Colombo. “Therefore I don't give a timeframe,” said the 38-year-veteran who was appointed army commander in 2005. The military in the last three months has stepped up an 18-month-old drive to wipe out the Tamil Tigers -- regarded as one of the world's most resilient guerrilla groups -- and end a war that has killed 70,000 since exploding in 1983. The Tigers want to establish a separate homeland for Sri Lanka's ethnic minority Tamils, in a nation that has been ruled by majority Sinhala-led government since independence from Britain in 1948. Ground troops have steadily fought through the northern jungles of the Indian Ocean island and smashed LTTE outposts, bunkers and trenches with air strike support and a naval push that has almost paralysed the marine “Sea Tigers” unit. “All that is being worked towards finally clearing them off altogether. They can't say ‘we are pulling back', or this is a tactical withdrawal. You can't have a tactical withdrawal for one and a half years,” Fonseka said. This week, the army said its soldiers had closed within 5.5 km (3 miles) of Kilinochchi, the insurgents' headquarters and a symbolic target for the military. “Just now they are fighting face-to-face, because we are fighting the Kilinochchi defense line, so the killing rate is very high. So I don't know how long they can afford to resist like this,” Fonseka said. Rebel founder and leader Velupillai Prabhakaran has moved east of there to somewhere inland from the Mullaittivu port, Fonseka said. He said that the military had already killed 9,000 LTTE fighters in the north. Independent confirmation of casualty numbers is difficult, since media access to the war zone is restricted and both sides for years have distorted the figures to their benefit. Despite the LTTE's vaunted squadrons of suicide fighters who wear cyanide capsules around their necks in case of capture, Fonseka said did not foresee them sustaining a conventional fight too much longer. “There are over 3,000 cadres, and I don't think they will fight to the last man. When it comes down to a certain level, they will try to go and mingle with the people or resort to other tactics like they are trying in the east,” Fonseka said. – Reuters __