Mindaugas Kulbis, File, Associated Press
This is a Friday, May 22, 2015 file photo of British Prime Minister David Cameron as he speaks during a media conference at the conclusion of the Eastern Partnership summit in Riga, Latvia. Cameron declared Sunday July 19, 2015 that Britain needs to take a greater role in destroying the Islamic State group in Syria, his most direct signal to date that he will seek to expand his country's role in supporting the United States and its allies.

LONDON — Prime Minister David Cameron is launching a five-year plan to defeat Islamic extremism, saying it's time to counter the ideology that has attracted so many young people to the Islamic State group.

In what is being billed as his most important speech on the subject, Cameron says the extremist ideology of the group, also known as ISIL, must be countered so Britain becomes a more cohesive nation in which young Muslims feel they have a stake.

Some communities in Britain have little attachment to the country and that makes them vulnerable to radicalization, Cameron says, according to excerpts released by his office. He delivered a harsh warning to young people who might consider joining the group.

"You won't be some valued member of a movement. You are cannon fodder for them. They will use you," he will say. "If you are a boy, they will brainwash you, strap bombs to your body and blow you up. If you are a girl, they will enslave and abuse you. That is the sick and brutal reality of ISIL."

Cameron is expected to announce a study designed to find ways to increase opportunities for young people from ethnic minorities and increase their integration in society.

Cameron also takes on the sensitive question of the role Britain's Muslim community should play in fighting Islamic State, saying extreme views such as believing in a "Jewish conspiracy" and opposition to "fundamental liberal values" are the gateway to violence.

"There are so many strong, positive Muslim voices being drowned out," he says. "Ask yourself, how is it possible that when young teenagers leave their London homes to fight for ISIL, the debate focuses on whether the security services are to blame?"

British police say some 700 potential terror suspects have traveled to Syria from Britain.