NEARLY two decades after their sudden and dramatic departure, American troops are preparing to return to Cambodia to help heal the scars left by two decades of warfare. About 60 US troops will arrive in Cambodia in July or August as part of a US$3 million (HK$25.5 million) mine-clearing programme. They will teach mine-clearing techniques to the Cambodian army. ''We will not be going out to clear any mines ourselves,'' said David Miller, a spokesman for the US Embassy in Phnom Penh. ''This is a training programme.'' He said the Americans would help train Cambodian forces in a variety of disciplines, from mine detection and disposal to medical treatment of injuries caused by mines. Information specialists will advise on programmes designed to raise awareness of mines. The mine-clearing activity is part of a part of a US$33 million United States aid package to Cambodia this year. The US has already provided US$6 million in de-mining aid to a country with more mines than anywhere else on Earth. Cambodian groups estimate clearing the mines may take 30 years. The Cambodia Mine Action Centre estimates there are eight to 10 million landmines still in place in Cambodia, roughly one for every Cambodian. The country is believed to have the highest proportion of amputees. In March, nations meeting at a Cambodian aid summit in Tokyo pledged US$15 million to aid the de-mining effort. American troops were sent to South Vietnam in the early 1960s, initiating more than a decade of controversial and unsuccessful American campaigns. Thousands of US troops aiding the Cambodian government of Lon Nol left shortly before its fall in 1975. Meanwhile, Cambodia's King Norodom Sihanouk has accused the Government of failing to run the country properly and has refused to sign into law a proposed bill outlawing the Khmer Rouge, Reuter news agency reported. A senior 14-member US delegation sent to Vietnam by President Bill Clinton pushed for faster progress towards accounting for missing soldiers during talks with Vietnamese officials.