BERLIN — Three Swiss engineers accused of participating in a global nuclear smuggling ring are set to avoid further prison time, in part because they helped the CIA bust the network that was supplying Libya's atomic weapons program.

Prosecution documents released Tuesday outline a plea bargain agreement under which Urs Tinner, 46, his brother Marco, 43, and their 74-year-old father, Friedrich, would accept the charges against them in return for prison terms that are shorter than the time they have already spent in investigative custody.

The documents also shed light on the U.S. intelligence agency's successful operation to destroy the nuclear smuggling network of Abdul Qadeer Khan, the architect of Pakistan's nuclear weapons program.

Friedrich Tinner had longstanding contacts to Khan dating back to 1975, according to Swiss prosecutors. The two continued to do business — with Tinner supplying equipment and expertise for uranium enrichment to Khan — even after Pakistan detonated its first nuclear bomb in 1998.

Khan built up an international network selling equipment to countries with nuclear weapons ambitions, including Libya and Iran. Prosecutors said all three of the accused were involved in the smuggling ring and supplied key equipment and blueprints for the production of gas centrifuges that are needed to enrich uranium to weapons grade levels.

Urs Tinner claimed in a 2009 interview with Swiss television that he had tipped off the CIA about a delivery of centrifuge parts destined for Libya's nuclear weapons program. The shipment was seized at the Italian port of Taranto in October 2003, forcing Libya to admit and eventually renounce its efforts to acquire nuclear weapons technology.

Swiss prosecutors said there was evidence the Tinners had cooperated with U.S. officials since at least June 18, 2003, and that the three engineers had manipulated the centrifuge parts intended for Libya to ensure they wouldn't function properly.

The CIA didn't immediately respond to a request for comment on the Tinner case. But the agency has said in the past that "the disruption of the A.Q. Khan network was a genuine intelligence success, one in which the CIA played a key role."

Federal prosecutors in Switzerland said the Tinners' cooperation with U.S. authorities and the U.N. nuclear agency should count as a mitigating factor in their sentencing. They added that the Swiss government's 2007 decision to destroy evidence in the case should also weigh in the men's favor, as the shredding of key documents made many of the allegations hard to prove. Prosecutors managed to recover some — but not all — of the files from Germany, where another Khan associate was sentenced in 2008.

The Tinners will appear before Switzerland's Federal Criminal Tribunal in Bellinzona for sentencing on Monday.