A U.S. court has ordered the continued detention of a Moroccan-born man arrested last week on suspicion of plotting a suicide bomb attack on the U.S. Capitol, the seat of Congress.

In a brief session Wednesday, the court in Alexandria, Virginia, ruled that 29-year-old Amine El Khalifi should remain in custody pending a grand jury's decision about whether there is enough evidence to bring him to trial. El Khalifi waived his right to challenge his detention.

Investigators say El Khalifi was arrested near the U.S. Capitol last Friday, wearing what he thought was a suicide bomb vest. He was charged with attempting to use a weapon of mass destruction.

Judge John Anderson said El Khalifi should be kept in detention because of the seriousness of the charges and the suspect's status as an illegal immigrant. The Moroccan overstayed a visa that he used to enter the United States in 1999 and never applied for U.S. citizenship.

The Federal Bureau of Investigation said El Khalifi received what he believed to be a suicide bomb vest and a gun from undercover agents posing as militants. It said the bomb and the gun were inoperable and the public was never in danger.

El Khalifi's arrest followed a months-long investigation in which the FBI said the suspect spoke to undercover agents about his desire to attack various Washington-area targets in revenge for what he perceived to be a U.S. war on Muslims.