WASHINGTON - US President-elect Barack Obama is formulating a plan to put Guantanamo detainees on trials on U.S. soil, which will lead to the closure of Guantanamo prison, a campaign promise he made, according to a media report. Harvard law professor Laurence Tribe, a legal adviser to Obama, was quoted by the Washington Post as saying Monday that among Obama aides, discussions about closing Guantanamo had been "theoretical" before the election, but it will now quickly become atop priority. Obama has described the infamous prison at U.S. naval base in Guantanmo Bay, Cuba, as a "sad chapter in American history" and insisted that the U.S. legal system could be enough to deal with the detainees. Now his aides are putting together proposals to release some detainees while sending others to trials on U.S. soil. However, a third group of high-risk cases may go before a new court designed to handle sensitive national security cases, according to advisers and Democrats involved in the talks. The potential move on Guantanamo is a contravention to the Bush administration, which established military tribunals to prosecute detainees and strongly opposes bringing prisoners to the United States. Analysts said Obama's plan could face opposition from Republicans who oppose bringing terrorism suspects to the United States, and from Democrats who oppose creating a new court system with fewer rights for detainees.