Radical preacher Abu Hamza al-Masri and three other terrorist suspects appealed to Britain's High Court Tuesday in a last-ditch bid to avoid extradition to the United States.

Al-Masri's lawyers said his health is deteriorating and that it would be oppressive to send him to the U.S. when he is in need of medical tests.

The lawyers seek a temporary injunction while an MRI scan is carried out. He has claimed severe health problems for at least four years.

Al-Masri, who turned London's Finsbury Park Mosque into a training ground for radical Islamists, is wanted in the U.S. on charges that include helping set up a terrorist training camp in rural Oregon

Last week a European court backed successive British judges in ruling that al-Masri, Babar Ahmad, Khaled Al-Fawwaz and Adel Abdul Bary could be sent to the U.S. to face charges.

Authorities in the U.S. have for years asked for the suspects to be handed over, but the process had been delayed because the men raised human rights objections.

Lawyers for al-Fawwaz argued that they'd uncovered "a substantial new body of evidence which casts doubt on the prima facie case" against their client — namely a voluminous British intelligence file.

In an argument before Justice Ouseley and Sir John Thomas, they also said that their client faced "the real risk of indefinite detention in solitary confinement" if he were sent to the U.S.

Arguments on behalf of the other suspects are expected later Tuesday.