"The U.S. counter-terrorism community supported efforts to draw links, to do intercepts and to monitor communications between Pakistan and Germany," a U.S. counter-terrorism official said.
The counter-terrorism official described the initial intercepts as "a key factor" that "helped build the case."
"It led to a very long period of surveillance, and the arrests." The official said the intercepts continued throughout the investigation.
This year, U.S. intelligence agents intercepted a key communication in which militant handlers in Pakistan asked for an update on the plot and pushed the suspects to move faster, German officials said.
At the start of the investigation, American intelligence also helped German police focus on the second convert, Daniel Schneider, a German official said.
U.S. intercepts detected the 22-year-old convert's e-mail communications with Pakistan and guided German police to him through a wireless signal he was pirating, officials said.
The suspects were simultaneously stealthy, brazen and reckless, officials said. The three evidently became aware of the constant surveillance and tried to thwart it, changing trains and dodging tails. They may also have noticed that the German and U.S. governments had issued several warnings during the year about increased terrorism risks, particularly threats posed by militants trained in Pakistan.
But when police this year confronted Schneider, and warned him that they knew what he was up to, he brushed them off, a German anti-terrorism official said. The trio plunged zealously ahead, the official said, apparently eager to die.
The suspects wanted to kill as many Americans as possible in the process, officials said. Probable targets of their alleged plan to build three car bombs were crowded bars, nightclubs, restaurants and airports. They chose Germany because it was their home turf and because of the large population of Americans around military bases.
"It's not just the military, but Americans in general," said a law enforcement official who asked not to be identified. "If they could have wiped out 1,000 American tourists, they would have been happy."
The three were unemployed; the two German natives collected welfare. Authorities said the trio claimed allegiance to the Islamic Jihad Union, an Uzbek group that in 2002 broke off from the Islamic Movement of Uzbekistan, an Al Qaeda ally. The IJU ran the Pakistani camp where they trained and oversaw their alleged mission, officials said.
