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 taskforce will report back to the two leaders within six months.
Mr Cameron also said Britain would deploy more unarmed drones to help ground forces tackle 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, Mr Obama hailed Mr Cameron as a "great friend" while the British prime minister said the US was a "kindred spirit".
BBC News - David Cameron and Barack Obama in anti-terror push
Hopefully the most effective part of their will come in May if Dave and his warmongering friends get given the order of the boot.
Joint defence being where the UK asks the NSA to collect data on UK citizens and send it to GCHQ and GHQ collects data on US citizens to send to the NSA. That way none can be accused of mass collection of data and surveillance on their own citizens. Oh hang on they already do that don't they.......
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 taskforce will report back to the two leaders within six months.
Mr Cameron also said Britain would deploy more unarmed drones to help ground forces tackle 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, Mr Obama hailed Mr Cameron as a "great friend" while the British prime minister said the US was a "kindred spirit".
BBC News - David Cameron and Barack Obama in anti-terror push
Britain and the US are to share expertise on preventing radicalism and tackling domestic "violent extremism".
Ahead of the talks, which lasted just over an hour, it was announced that the UK and US are to carry out "war game" cyber attacks on each other as part of a new joint defence against online criminals.
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