At a joint news conference between the two leaders, Clinton assured his guest that "the United States is not trying to duck its responsibility."
The president said Americans were "profoundly regretful and apologetic for what has occurred to the families and all of the people of Italy." He reiterated the United States remained determined to assess responsibility for the accident.
But D'Alema was not reassured by Clinton's words.
"We shall say we are satisfied when whoever is responsible for what happened is found guilty and punished," D'Alema said. "With so many casualties and so many deaths, you can hardly ever say you are satisfied."
D'Alema also said the situation had strained U.S. relations with Italy, a NATO ally.
Clinton said Defense Secretary William Cohen would meet with his Italian counterpart to review operation changes designed to avert similar accidents.
"We are horrified and heartbroken by what happened and we will do our best to make sure something like that doesn't happen again," Clinton said.
Both leaders noted there was further judicial action pending and they gauged their comments so as not to influence it.
On Thursday a military jury in Camp Lejeune, N.C., cleared Ashby of 20 involuntary manslaughter charges in the accident of Feb. 3, 1998.
During a training flight in the Italian Alps, Ashby flew into two cables holding up a gondola packed with tourists who were preparing to ski. Eight Germans, five Belgians, one Austrian, one Dutch person, two Poles and three Italians perished. The incident touched off a wave of criticism that the Marine crew was speeding and showing off, in complete disregard for the civilians around them.
"With that kind of a massacre, with so many casualties, I think it is a duty to ensure... that justice is done, and that is what we are asking for," D'Alema said. "Certainly this is not an Italian problem, nor does it concern Italy and U.S. relations alone."
Shortly after the tragedy last year, Defense Secretary William Cohen authorized a discretionary payment of $5,000 to each victim's family to cover immediate transportation and burial expenses. The U.S. government has reimbursed Italy for the $60,000 it paid to the survivors of each victim.
Half of the 20 victims' estates have filed wrongful death claims with the Italian ministry of defense, ranging from $812,000 to $5.4 million, and all 20 families have hired attorneys, with intentions of filing claims to be processed by the Italian government.
The State Department said Thursday the United States will continue to work closely with Italan officials to ensure the claims are handled expeditiously.