The court on Tuesday also handed down jail terms ranging from six to 15 years for two other men convicted in the conspiracy.
Laurence Foley, 60, an Amman-based administrator for the US Agency for International Development, was gunned down outside his home in the capital on 28 October 2002.
Colonel Fawwaz Buqur, the court's president, acquitted the 11th defendant, Numan al-Hirsh, saying there was no evidence to implicate him in the conspiracy.
The guilty verdicts can be appealed.
Among those sentenced to death was Jordanian fighter Ahmad al-Khalaylah, better known as Abu Musab al-Zarqawi, who is thought to be a close associate of al-Qaida chief Usama bin Ladin.
Al-Zarqawi, whose whereabouts is unknown, was among six defendants who were tried in absentia.
The five defendants in custody, standing in the dock wearing dark blue prison uniforms, shouted "Allahu Akbar," or "God is greatest," and "this verdict is unfair" as Buqur read the verdict in a small courtroom, guarded by armed military policemen.
Outside the courtroom, a military helicopter hovered overhead during the hearing.
Foley's death was the only attack linked to the Jordan conspiracy, which allegedly targeted unspecified American and Israeli interests in Jordan.
"As a result of their investigation, they discovered that among the targets these individuals were looking at was the American embassy"
State Department spokesman
Jordan signed a peace treaty with Israel in 1994.
Eleven Libyan, Syrian, Palestinian and Jordanian Islamists had been charged. Their trial began in the military State Security Court 10 months ago.
The five in custody, including the Libyan national, told the court their guilty confessions had been extracted under duress.
Two of the accused produced witnesses who testified the men were not at the crime scene when Foley was killed.
Last week, authorities said they arrested several suspects who had entered the kingdom from Syria to carry out attacks against government ministries and other targets. At least three others in the latest alleged plot are still at large.
Also on Tuesday, it was announced that Jordanian authorities thwarted a plan by members of the al-Qaida network to attack the US embassy in Amman last week.
A file photo showing the US
embassy in Amman
State Department spokesman Adam Ereli said the plot had been uncovered after the arrests of members of a cell reportedly linked to al-Zarqawi.
"The Jordanians captured some individuals who they believe were affiliated with the Zarqawi al-Qaida network," he told reporters.
"As a result of their investigation, they discovered that among the targets these individuals were looking at was the American embassy," Ereli said, noting that the Jordanian investigation was continuing.
A senior State Department official said Washington was taking
the threat "very seriously" given the nature of the detained
suspects. "These are really bad guys," the official told reporters on condition of anonymity.
On Monday, the US embassy in Amman issued a notice to Americans in Jordan advising them of the threat and urging them to stay abreast of developments related to the security situation.