London, England (CNN) -- Allied forces in Afghanistan don't have to beat al Qaeda, just contain the terrorist organization, the new chief of Britain's armed forces said in a newspaper interview published Sunday.
Gen. David Richards told the Daily Telegraph that a victory over radical Islamist movements like al Qaeda is "unnecessary and would never be achieved." But they could be contained "to the point that our lives and our children's lives are led securely," Richards said.
And in an interview with the BBC on Sunday, Richards added, "I don't think you can probably defeat an idea."
"This is going to be, in that sense anyway, a generational issue, because a lot of it's to do with understanding, education, things like democracy and how long those take to get embedded in those states where currently it's clearly not on the agenda," he said.
The war in Afghanistan was launched after al Qaeda's September 11, 2001, attacks on New York and Washington. More than 340 British troops have been killed in the conflict, with the latest fatality reported Sunday -- Britain's annual holiday to commemorate its war dead.
Richards told the Telegraph that Britain's sacrifice "has been worth it," and that progress was being made in the now-9-year-old war.
"If I thought for one minute that the majority of the Afghan people didn't want us any more -- then I and everyone else would say that it's time to go, we've failed," he said. "But there is no indication of that. The vast majority do not want the return of the Taliban, and it must be in our strategic interest to see that whole region stabilised before we eventually go, which we will do."
Prime Minister David Cameron has said that British troops must be out of Afghanistan before the next general election, scheduled to be held in 2015. Cameron said in June that he preferred "not to deal in too strict timetables," but said the goal is "not a perfect Afghanistan, but some stability in Afghanistan, and the ability of the Afghans themselves to run their country so we can come home."
Richards told the Telegraph that there was "no dispute or disagreement" over ending Britain's combat mission in Afghanistan by that date. But he added. "We are equally clear that we have got to support the operation thereafter to make sure that our legacy is an enduring one."
CNN's Bharati Naik contributed to this report.