Ubaidat confirmed on Saturday Jordanian press reports of the charges, but did not give further details. 

The dailies al-Rai and al-Dustour said the four men were accused of possessing an illegal automatic weapon and conspiring to carry out attacks on Americans, especially those living in the Azraq area where Jordan's biggest air base is located, 70km northeast of Amman and 240km from the Iraqi border. 

Three of the men are in custody and have admitted to plotting such attacks, but the fourth, a finance ministry employee, is on the run, the papers said. The charges carry the death penalty. 

In 2002, the government denied speculation Jordan was allowing US troops to use the Azraq base to prepare for an attack on Iraq and opened the base to journalists. 

'Jihad and martyrdom'

Al-Rai said the suspects had practised using a machine gun at a farm owned by the uncle of one of them, and watched video footage of "resistance operations."

They became strict Muslims in 2003 and thought of "jihad and martyrdom to repent their sins," it reported. 

Eleven Islamist opposition figures are on trial in Jordan on charges of killing a US diplomat in Amman in 2002. The charges carry the death penalty, but this can be appealed.