WASHINGTON (AFP) - US President George W Bush said he hopes his successor Barack Obama will carefully weigh keeping controversial interrogation tactics and other policies that his administration put in place to fight the "war on terror". Bush said his approach to fighting terror threats, including harsh interrogation tactics, was justified to protect the United States. "I would hope that the team that has the honour of serving the country will take a hard look at the realities of the world and the tools now in place to protect the United States from further attack," Bush said on Fox News Sunday, referring to the next administration. "I would hope they would take a sober assessment, and I believe they will." Bush, who will leave office on January 20 when Obama takes over the presidency, said that "we better have tools in place that are legal and that can help us protect the American people from an enemy that still exists." "And my concern is not for President-elect Obama, because I'm confident that he understands the nature of the world and understands the need to protect America," Bush said of the President-elect, who is under pressure to make a break with the current administration's counter-terrorism policies. "But I am concerned that America at some point in time lets down her guard. And if we ever do that, the country will become highly vulnerable." Bush strongly defended his use of presidential authority, despite criticism from lawmakers and rights groups that he overstepped the country's Constitution and permitted the torture of terror suspects after the attacks of September 11, 2001. "My presidency was defined by the attack on the country and, therefore, I used the powers inherent in the Constitution to defend this country." He rejected allegations his administration approved the use of torture in questioning terror suspects. "I firmly reject the word 'torture'," said Bush, adding that his administration had always acted legally and had kept Congress informed. Some lawmakers disagree, saying while they were notified of counter-terrorism measures their objections were ignored. Bush said his approach to fighting terror threats, including harsh interrogation tactics, was justified to protect the United States. "My view is - is that the techniques ... were necessary and are necessary to be used on a rare occasion to get information necessary to protect the American people." The tactics produced valuable intelligence when used on the alleged mastermind of the 9/11 attacks, Khalid Sheikh Mohammed, Bush said. "We gained good information from Khalid Sheikh Mohammed," he said. Outgoing vice-president Dick Cheney has confirmed that Khalid and two other suspects were subjected to "waterboarding" or simulated drowning, which is widely criticized as torture, and that other detainees were exposed to harsh interrogation tactics. The administration's counter-terrorism measures were always carried out with "a legal basis," Bush said. "Otherwise, we would not have done it." Bush revealed that he plans to write a book after leaving office later this month, but admitted he's not yet sure what it will be about. "I'm not quite exactly sure what it's going to be, but I'm toying with the idea of maybe describing the toughest decisions I had to make as president and the context in which I made them," Bush said. "What's evident to me is that it is very hard for people to remember what life was like a mere four or five years ago, and it could be very important for me to recreate the environment in which I had to make certain decisions, particularly the environment of right after September the 11th, 2001," he said. Bush, who throughout his eight years in office has frequently been chided in the media for lapses of eloquence when he expressed himself, declined to set a timeframe for his writing project. "I could say two years and it could be four. I'd like to get her done," he said. "I am a type 'A' personality. I require things to do. Once I get going on this book, I'll be able to get her done," he said. In addition to writing, Bush said he was planning on being "fairly footloose for a while" after he hands over the presidency to Democrat Barack Obama on January 20. "I can remember with a great sense of anticipation coming to Washington, DC, to be the president of the United States, and I have the same sense of anticipation heading out of political life, but without the sense of gravity," he said. "So I'm going to be fairly footloose for a while." Bush said one of his main tasks will be developing a policy centre associated with a presidential library in Texas. "I want to promote a set of values that I think are very important for the country," he said.