The suit also blames the Palestinian authorities for refusing or ignoring American and Israeli demands to prevent further terrorism. It further alleges that Palestinian officials provided Hamas with a "safe haven and a base of operations" and permitted and/or encouraged Hamas to "operate freely and conduct activities in the territory under their control."

The Palestinians turned down repeated requests by the Israeli government to surrender terrorist suspects and even employed some suspects as policemen or security officials, according to the plaintiffs, which include the couple's two children, ages 4 and 5.

The suit is based on a statute that gives U.S. federal courts jurisdiction over cases of American citizens who are injured in foreign countries by acts of terrorism. Survivors or heirs of the victim may sue in any U.S. District Court.

Congress enacted the law after victims of the 1985 PLO hijacking of the Achille Lauro cruise ship had difficulty with their civil suits.

However, even if the Ungar family wins its case, any judgment that is awarded may be difficult to claim.

A similar lawsuit was brought against Iran by the family of Alisa Flatow, a 20-year-old New Jersey student killed in a bus bombing in 1995. The Flatows won a $247.5 million judgment, but have not been able to collect any damages, in part because of opposition from the Clinton administration.