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A defense attorney for an Oregon terrorism suspect used her cross-examination of an FBI agent on Wednesday to raise the idea that Mohamed Mohamud was a naive, inexperienced teenager manipulated into taking part in a phony plot to detonate a bomb.

The agent, who had posed as an al-Qaida terrorist, was cross-examined by defense attorney Lisa Hay during the third day of testimony in Mohamud's trial. He acknowledged that Mohamud had trouble with relatively simple tasks, such as renting a storage shed and buying items to be used in the making of the bomb.

The device was to be set off at a Portland Christmas tree-lighting ceremony in 2010. But it was a fake, supplied by the undercover FBI agents.

The agent, who used the pseudonym Youssef, also testified that he suggested topics for Mohamud's so-called "goodbye video." The video, shot at the behest of the agents, was to be shown after Mohamud committed the crime and fled the country.

The 21-year-old Mohamud is charged with attempting to ignite a weapon of mass destruction, which could put him in prison for life.

Hay said during her questioning that Mohamud "didn't have much money until you came into his life," and that the older undercover agents provided financial and emotional support — and food — at a time when Mohamud's parents were separated and a close friend had gone to Afghanistan.

Youssef testified that Mohamud shed tears during their initial meeting, something the agent attributed to the teen's loneliness because of his friend's departure.

When the agent met Mohamud, the young man was living with his mother. Hay played wiretapped recordings in which the agent, in the attorney's view, spoke to him like a child.

"No offense, but to us you're a kid," the agent said on one recording.

The agents eventually wanted Mohamud to get his own apartment because it would make the sting operation easier to facilitate. They gave him almost $3,000 to rent a place and buy bomb-making materials.

Mohamud wrote in a September 2010 email that he had never rented an apartment before and asked if they or a "brother" might co-sign.

"Kind of a clueless idea to think al-Qaida would co-sign," Hay said. "Don't you agree?"

The attorney also played recordings in which the agents asked Mohamud to rent a large storage shed in which to build the bomb.

Youssef testified the FBI assigned such tasks to test the Mohamud's resolve. In this test, however, Mohamud initially didn't understand what type of storage unit the agents wanted, and then took a month to follow through. The agent acknowledged that he and another agent had to prod Mohamud, eventually giving him the name of a storage company and driving by.

"Not much of a test if you're pointing out the right one," Hay said.

Under re-direct questioning by prosecutor Ethan Knight, the agent said the FBI did not have to manipulate Mohamud to get him to participate in a plot to potentially kill thousands of people.

"He knew what he wanted to do, and it was to kill Americans," Youssef said, adding that this was: "Before I met him."