The US and UK vow to fight “poisonous and fanatical” ideology of the terrorists
Britain and the US are to share expertise on preventing radicalism and tackling domestic “violent extremism”.
Prime Minister David Cameron announced the move following talks with President Barack Obama at the White House, warning that they both faced a "poisonous and fanatical ideology".
The task force will report back to the two leaders within six months.
Cameron also said Britain would deploy more unarmed drones to help ground forces tackle the Islamic State.
The Prime Minister is on a two-day visit to Washington for talks with President Obama, likely to be his final Washington visit before the UK general election in May.
At a press conference in the White House, Obama hailed Cameron as a "great friend" while the British PM said the US was a "kindred spirit".
The talks between the two leaders came a week after the deadly terrorist attacks in Paris in which 17 people were killed.
Concerns over additional attacks by Islamic extremists intensified on Thursday after an anti-terror raid by police in Belgium to pre- empt what officials called a major impending attack.
UK police have said there is "heightened concern" about the risk to the UK's Jewish communities and are considering stepping up patrols in certain areas.
Cameron said it was a "sensible, precautionary" measure taken to "reassure those communities".
Cameron said: "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."
Assistant Commissioner Mark Rowley, the UK's police lead for counter-ter- rorism, has said police have been reviewing their own security since the Paris attacks.
"We are also considering what further measures we might put in place to enhance the security of police officers, given some of the deliberate targeting of the police we have seen in a number of countries across Europe and the world," he said.
"Chief constables across the country are reviewing how to strengthen the protection of their officers from such attacks."
President Obama said the US, UK and its allies were "working seamlessly to prevent attacks and defeat these terrorist networks".
Asked whether an attack was "imminent" in Britain, Cameron said the terror threat level, set independently by the Joint Terrorism Assessment Centre, was currently at "severe" - meaning an attack is "highly likely".
He warned that the fight against terrorism "is going to be a long, patient and hard struggle" but added that "we are quite convinced we will overcome it".