US President Barack Obama and British Prime Minister David Cameron vowed to take on "the poisonous ideology" of Islamic extremists and said intelligence agencies must be allowed to track militants online despite privacy concerns.
Obama and Cameron held two days of White House talks amid increasing concern in Europe about the threat posed by extremists after 17 people were killed in Paris attacks and Belgian authorities engaged in a firefight with terror suspects.
"We face a poisonous and fanatical ideology that wants to pervert one of the world's major religions, Islam, and create conflict, terror and death. With our allies, we will confront it wherever it appears," Cameron told a joint White House news conference with Obama after their talks.
Obama said he and Cameron accepted that intelligence and military force alone would not solve the problem, and they would work together on "strategies to counter violent extremism that radicalizes recruits and mobilizes people, especially young people, to engage in terrorism."