By Teresa Carson

PORTLAND, Oregon (Reuters) - Lawyers for the accused would-be bomber of an Oregon Christmas tree-lighting event sought on Wednesday to cast their Somali-born client as an emotionally fragile teenager prone to manipulation by undercover agents who coached him in planning an act of mass murder.

One of those agents, testifying under defense cross-examination in federal court, acknowledged that the target of the FBI's sting operation was a lonely, financially strapped student whose parents' marriage was unraveling.

Mohamed Osman Mohamud, a naturalized U.S. citizen and former Oregon State University student, faces life in prison if convicted of attempting to use a weapon of mass destruction to blow up the ceremony in Portland in November 2010. He was 19 at the time.

Defense attorneys argued last week at the start of the trial that their client was accused of a crime that was essentially the creation of overzealous law enforcement officers.

Mohamud, after months spent in the frequent company of two FBI agents posing as al Qaeda operatives, was arrested when he tried to use a cell phone to remotely detonate an artificial car bomb supplied by the agents, according to trial testimony.

The fake bomb was planted in a van left parked near a downtown Portland square lined with shops and offices and crowded with thousands of people attending an annual Christmas tree-lighting ceremony the day after Thanksgiving. No one was hurt, and authorities say the public was never in real danger.

After two days on the witness stand recounting events leading up to Mohamud's arrest, the FBI agent identified in court only by his undercover name, Youssef, took questions from defense lawyer Lisa Hay as she tried to paint the accused as someone especially vulnerable to entrapment.

Youssef testified that he and a fellow agent who went by the pseudonym Hussein were aware that Mohamud was lonely, that he had little money and that his family was in distress. He said Mohamud wept during their first meeting and that he heard his partner tell Mohamud on many occasions, "I love you."

AGENTS GAVE DEFENDANT CASH

At one meeting, the two agents gave Mohamud some $2,800 in cash to rent an apartment in Corvallis, Oregon, near campus, lecturing him not to spend the money frivolously, Youssef told the jury.

Youssef also acknowledged that he and Hussein had coached Mohamud on what he should say in the videotaped "goodbye" message they filmed of him weeks before the planned attack, and even suggested he wear the red-and-white checkered scarf that adorned his head in the video.

In the video, shown to the jury by prosecutors on Tuesday, Mohamud is seen solemnly saying to the camera: "A dark day is coming your way ... your people will not remain safe." Continued...