Desperate to cooperate after his arrest, a confessed Pakistani American terrorist tried to help U.S. authorities engineer the arrest of a suspected mastermind of the 2008 Mumbai attacks, and he proposed setting up another kingpin for a missile strike, he testified Tuesday.

David Coleman Headley, who has pleaded guilty in the Mumbai case and a plot against Denmark, said that during two weeks of interrogation in October 2009 he worked with FBI agents to try to lure Sajid Mir, a chief of the Lashkar-i-Taiba militant group, out of Pakistan so he could be arrested. The attempt failed, Headley testified in federal court, and Mir remains a fugitive.

Headley also offered to travel undercover to Pakistan’s tribal areas, to present Ilyas Kashmiri, an al-Qaeda-connected leader indicted in the Denmark plot, with an ornate sword — perhaps concealing a homing device that could be used in a U.S. missile attack.

Headley revealed Tuesday that Kashmiri wanted to assassinate the chief executive of Lockheed Martin, which manufactures the Predator drone, as retaliation for the missile strikes that have killed scores of militants in Pakistan.

“Kashmiri was working on a plan,” Headley testified. “He said he knew people who had already done surveillance. And he asked if weapons were available in the U.S.”

Headley, who did not further describe the details of the plot, met with Kashmiri twice in Pakistan in 2009, according to his confession. U.S. officials declined to comment on Headley’s mention of a plot targeting Lockheed CEO Robert J. Stevens. Lockheed officials also declined comment.

Kashmiri, who wields increasing influence in al-Qaeda, was behind a plan last fall to carry out Mumbai-style shooting attacks in Europe, counter-terror officials say. But it would be a new and troubling development if he had operatives working on a plot in the United States.

Tuesday was Headley’s last day as the star witness against his boyhood friend Tahawwur Rana, who is charged with material support of terrorism for allegedly aiding Headley’s reconnaissance in Mumbai and Denmark. Throughout five days of testimony, a question has hovered over the courtroom: Is Headley telling the truth?

The trial could have a profound impact on the troubled relationship between the United States and Pakistan because Headley has asserted that Pakistani intelligence officers played a key role in the attacks.

By his own admission, Headley has credibility problems.

He is a former heroin addict and drug smuggler. He has juggled allegiances to the Drug Enforcement Administration, Lashkar-i-Taiba, al-Qaeda and Pakistani intelligence. He has maneuvered among overlapping relationships with three wives. To save himself from the death penalty, he has pleaded guilty to scouting for the Mumbai attacks and a plot in Denmark, and he is now the star witness against Rana, his boyhood friend and alleged accomplice.

When the FBI arrested Headley in 2009, investigators were stunned by his insider’s knowledge of the Mumbai plot, which killed 166 people, including six Americans. They worried, however, that his talent for deception could result in disaster in court, so they worked to confirm as much of his account as they could.

They scoured his computer for information. They analyzed his phone, travel and credit card records. They pored over the intelligence haul gathered while shadowing him and monitoring his communications for at least two months before his arrest. They compared his story to the results of investigations in India, Pakistan, Denmark, Britain and elsewhere.

As a result, the case unfolding in Chicago consists of far more than Headley’s word.

When Headley testified last week that he met a mastermind in Karachi as Lashkar prepared to deploy a maritime attack team, the prosecution produced his hotel bill from that date in Karachi. When Headley described scouting targets in Denmark, prosecutors showed the jury his surveillance video of those targets. At some points, his testimony and the supporting evidence flowed together to create an almost real-time picture of his activity.

Headley’s testimony about Pakistan’s Inter-Services Intelligence agency (ISI) focused on a shadowy figure known as Maj. Iqbal. Headley says Iqbal was his ISI handler, although he admits that he does not know Iqbal’s real name.

Pakistani officials have denied that the ISI played any role in the Mumbai attacks and that Iqbal was a serving intelligence officer. Some question whether Iqbal really exists.

But U.S. prosecutors are so convinced that Iqbal is real that they took the diplomatically explosive step of indicting him last month. They have done their best to bring him to life in the courtroom, displaying his e-mail exchanges with Headley and Rana. According to intercepted phone calls and other evidence Headley spent months talking with associates about Iqbal and other ISI officers.

In September 2009, Headley received a call in Chicago from his brother in Pakistan saying that Iqbal had come to Headley’s house in Lahore looking for him, according to wiretap evidence. Phone and e-mail evidence also backs Headley’s testimony that he knew another ISI officer identified as Maj. Sameer Ali.

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