A Moroccan man was arrested near the US Capitol on Friday wearing a vest he believed was full of al Qaeda-supplied explosives and charged in an attempted suicide bombing of Congress, the Justice Department said.

Amine El Khalifi, 29, an illegal immigrant who lives in Alexandria, Virginia, was charged with attempting to use a weapon of mass destruction against property owned and used by the US, intending to detonate a bomb and to shoot people, the department said.

He was arrested by the FBI and the US Capitol Police in a parking garage just a few blocks from the Capitol. The object of a lengthy undercover FBI investigation, El Khalifi later appeared in federal court in Virginia and faces up to life in prison if convicted.

US law enforcement officials said there never was any threat to the public. The explosives in the suicide vest and the gun he had been given by the FBI had been rendered inoperable and posed no danger to the public.

The officials said the arrest capped a year of monitoring by law enforcement authorities.

There have been a number of undercover operations in the Washington, DC, area in recent years in which suspects thought they were plotting to carry out terrorism attacks, but in reality were being monitored by FBI agents and posed no danger.

El Khalifi thought he was dealing with members of al Qaeda, but they were really undercover agents, officials said.

'The complaint filed today alleges that Amine El Khalifi sought to blow himself up in the US Capitol building,' said US Attorney Neil MacBride. 'El Khalifi allegedly believed he was working with al Qaeda and devised the plot, the targets and the methods on his own.'

Sergeant Kimberly Schneider, a spokeswoman for the US Capitol Police, said there was no danger to the public or members of Congress.

According to court records, El Khalifi entered the United States in 1999 on a visa, overstayed it and never applied for US citizenship.

According to an FBI affidavit, in January 2011, a confidential source reported to the FBI that El Khalifi met with other individuals at a residence in Arlington, Virginia.

During the meeting, one person produced what appeared to be an AK-47, two revolvers and ammunition. El Khalifi allegedly expressed agreement with a statement by the individual that the 'war on terrorism' was a 'war on Muslims' and said the group needed to be ready for war, according to the affidavit.

Last month, El Khalifi said he had changed his plans and wanted to conduct a suicide attack at the Capitol, rather than his original plan to bomb a restaurant, according to the affidavit.

The affidavit said El Khalifi detonated a test bomb just over a month ago in a quarry in West Virginia and that he 'expressed a desire for a larger explosion in his attack' at the Capitol.

He selected February 17 as the day of the operation, according to the affidavit.

The affidavit said that during the past month El Khalifi traveled to the Capitol on multiple occasions to conduct surveillance, choosing the spot where he would be dropped off to enter the building, the specific time for the attack and the methods to avoid attracting the attention of law enforcement.-Reuters