"I became very radical in my views," he said.
While sitting in a car outside a Queens mosque, the three men "made a covenant to go to Afghanistan and fight with the mujahedeen against American forces," he said.
The men traveled in 2008 to Pakistan, where they met al-Qaida recruiters who told them they would be better suited for a suicide mission in the United States, the witness said. They were driven 10 hours away to a training facility protected by 20-foot mud walls. After morning prayers, English-speaking terrorists taught them how to use grenades, AK-47s and other weapons, he said.
Zazi also is expected to testify about how, after relocating to the Denver area, he cooked up explosives and set out by car for New York City in September 2009 to carry out the attack. He was arrested after abandoning the plan and fleeing back to Colorado.
Another possible witness is Bryant Neal Vinas, a Long Island man who joined al-Qaida around the same time as the other men. Officials have credited Vinas with providing key intelligence about the terror group since his capture in 2008.
Meanwhile, Britain's Crown Prosecution Service said Monday that it had struck a rare deal with a convicted terrorist to provide possible testimony or other evidence for Medunjanin's trial. Saajid Badat, who was jailed in Britain in 2005 for his role in a 2001 plot to down an American Airlines flight from Paris to Miami with explosives hidden inside shoes, had his jail term cut from 13 years to 11 years under the agreement.
Associated Press writer David Stringer in London contributed to this report.