Stuttgart - A German court sentenced a 65-year-old engineer to five-and-a-half years in prison Thursday for advancing Libya's former plans to make its own atomic bombs.

Defence lawyers said they expected this would mean he could be set free immediately, after deduction of automatic parole and credit for 21 months he spent in pre-trial custody and for the months spent in court.

Earlier this month he admitted he gave advice on how to build a piping system for a uranium-enrichment plant.

Prosecutor Wolfgang Siegmund said earlier Thursday the defendant helped Libyan interests, but had not been a member of an international network of nuclear smugglers led by the rogue Pakistani scientist Abdul Qadeer Khan.

US and German intelligence agents uncovered the plans to export the piping system, earlier media reports said. Libya has since abandoned its nuclear ambitions.

The defendant was convicted of breaching German laws restricting exports of militarily useful products.

A previous trial which began in July 2006 had to be called off after the bomb plans - regarded as evidence by the defence team - were shredded by Swiss authorities.

Under an agreement with the defence to settle with a compromise, prosecutor Siegmund dropped an allegation that the defendant was the builder and supplier of a gas ultra centrifuge system to refine uranium for Libya's bomb.

Siegmund, who pressed for a six-year prison term, said Thursday that Libya in fact came nowhere close to making its own bomb, but the defendant's actions had endangered international peace.

The Abdul Qadeer Khan network allegedly supplied equipment to Iran, Libya and North Korea using front companies in South Africa and Malaysia. (dpa)