Ronald Grecula, who spent some two years in prison in Malta after abducting his children and fleeing to Malta, received a five-year United States Federal jail term on Friday for offering to build and sell bombs to a terrorist organisation he believed was affiliated with Al-Qaeda.

But the individual he thought was a representative of the terrorist organisation was in fact an undercover agent with the federal anti-terrorism task force.

The task forced had been tipped off about Grecula by a confidential informant who had met Grecula when he was in prison in Malta after bringing his children to Malta in 2000.

In 2002, in a widely publicised court case, the Maltese courts awarded Grecula’s wife custody of the two children, then 10 and three years old, and Grecula was eventually deported to the US.

The informant, whose identity has been concealed, later told US authorities that while in Maltese prison Grecula had asked him for help finding a terrorist group that wanted to purchase a bomb, saying he would fly anywhere in the world to build a prototype to demonstrate his capabilities.

The informant is said to have later been deported to Guyana, but had kept in touch with Grecula and eventually alerted the FBI about his intentions.

The sting operation caught Grecula, 69, from Pennsylvania, offering to build a bomb that would destroy everything within more than a half-mile, in return for the terrorist organisation helping him regain custody of his children.

From transcripts of the sting meeting, Grecula, a pilot, offered to teach the “operatives” how to fly airplanes and led a toast to “killing Americans”. He even suggested several targets, including the Federal Reserve in New York and unidentified buildings in Washington DC, and the Super Bowl.

“According to the (confidential informant), Grecula had asked him/her to find someone for whom he could build a large bomb and be paid for it,” the FBI affidavit reads. “Grecula specifically referenced al-Qaeda and Osama bin Laden, but confided he would be willing to build bombs for other groups who could pay him.”

The informant made several FBI-monitored phone calls in which Grecula discussed the specifics of bomb making. The informant then put Grecula in contact with the undercover agent, according to the affidavit.

In transcripts of conversations with the informant and the agent, Grecula describes himself as a researcher with training in engineering and experience with new energy technologies capable of producing enormously powerful blasts.

Having originally pleaded guilty in September to charges of attempting to provide material support and resources to a foreign terrorist organisation, Grecula tried to revoke the plea this week before judgement but was turned down.

Grecula’s defence had maintained he was mentally ill and his stories of building hydrogen chlorine bombs were nothing but “gibberish”. Grecula underwent several psychological exams while in prison and was found to be delusional and suffering from bi-polar disorder, it was unsuccessfully argued.