US President Barack Obama and British Prime Minister David Cameron have expressed determination to confront militant group Islamic State (IS).
In their joint article in the Times, the British PM and the US president said those who called for isolationism "misunderstood the nature of security in the 21st Century", reports BBC.
They warned against an "isolationist approach".
"Developments in other parts of the world, particularly in Iraq and Syria, threaten our security at home," they said.
They also said the UK and US would "not waver in our determination to confront" IS, adding: "Countries like Britain and America will not be cowed by barbaric killers."
David Cameron has said he will not rule anything out with regards to military action against Islamic State, which is holding a Briton hostage.
But speaking ahead of a Nato summit in Wales, the prime minister said any action, including military force, must not be seen as "Western intervention over the heads of neighbouring states".
The US is using air strikes against IS but Britain has not yet done so.
Meanwhile, there have been growing calls for talks with Syria's President Assad to reinforce efforts against the militant group.