Home Secretary David Blunkett has defended the UK's actions over radical Muslim cleric Abu Hamza, who is facing 11 terror charges in the US.
Abu Hamza, pictured here in May, was remanded in custody
The US aims to get the preacher extradited to face charges including hostage taking and supporting al-Qaeda.
"Obviously if we had that evidence and it related to our country, we would have been able to take action through our courts," Mr Blunkett told the BBC.
He said UK information had led to a bid to withdraw Mr Hamza's citizenship.
"There has been controversy about what Abu Hamza has been doing, what he has been up to, what he has been saying in particular," Mr Blunkett told Radio 4's Today programme.
That had prompted the withdrawal of citizenship currently being fought by the cleric through the courts, the home secretary said.
"I have taken the necessary action that I believe is appropriate to expel him from our country."
Mr Hamza has said he will contest extradition, following his arrested at his Shepherds Bush home on Thursday.
About 50 of his supporters gathered for Friday prayers outside the Finsbury Park mosque where he used to preach, to express their support.
US Attorney General John Ashcroft, announcing the charges in New York, said the cleric could face the death penalty or life imprisonment if found guilty.
But under current UK law, Britain must seek US agreement that no death penalty will be sought before any extradition is approved.
Former assistant US attorney-general Victoria Tonsing said: "If you ever broke a promise like that, there would never be another extradition."
Mr Hamza is accused of acting as an intermediary with a terrorist group which took 16 tourists hostage in the Yemen, six years ago.
Three British tourists and one Australian died when they were used as human shields during a shoot-out with Yemen rescuers, it is alleged.
The US claims it has linked Mr Hamza to the hostage-taking by monitoring satellite phone calls.
It also alleges Mr Hamza provided support and resources for terrorists, particularly al-Qaeda, and attempted to establish a terror training camp in Bly, Oregon.
'Victim of belief'
Muslim cleric Sheikh Omar Bakri told Today: "Anybody who looks into the case will see Abu Hamza is a victim of what he believes. The US Government has failed to find al-Qaeda members, they turn against the sympathisers of al-Qaeda.
"The British Government and British police never found any evidence against Abu Hamza, who was living on their own doorstep."
Mr Hamza gained UK citizenship through marriage in 1981.
He regularly preached at Finsbury Park until February 2003 when the Charity Commission banned him for using his position for "personal and political" purposes.
But he has continued preaching outside the mosque.