But questions remain over the mission's future, as NATO allies criticize Italy's handling of a recent hostage crisis.
Prodi's center-left cabinet needed support from an opposition party and faced criticism from its own communist allies, but in the end the former European Commission president hailed the vote as a major step forward.
"This vote is a turning point -- remember that," Prodi said. "This vote is a turning point. The opposition is divided. The majority is united. That seems to be quite a difference to what was being said previously."
Last month, Prodi was forced to resign after a defeat on foreign policy in parliament. He stayed on at the president's request, and the March 27 vote has given his government -- and Italy's Afghan mission -- a new lease of life.
"Yes, [the Italian mission] is secure until the end of the year," said Giovanni Gasparini, a defense analyst at Rome's Institute of Foreign Affairs. "We have both the money and the political will [to keep it going]."
Under Fire For Hostage Deal
The Senate vote was complicated by controversy over a prisoner swap that Rome engineered last week to secure the release of Daniele Mastrogiacomo, a well-known Italian journalist whom the Taliban had held hostage for 15 days.
The United States, Germany, Britain, and the Netherlands denounced the deal, under which five jailed Taliban -- three of them high-level -- were freed in exchange for Mastrogiacomo. They said it put NATO troops in danger and rewarded kidnappers.
The deal also failed to secure the release of Mastrogiacomo's Afghan interpreter, while his driver was beheaded by the Taliban.
The incident last week sparked antigovernment protests in Helmand Province, where the kidnapping occurred.
"In exchange for Afghans, they have released the foreigner," one demonstrator told RFE/RL's Afghan Service. "What kind of government is this? This is not a government. It is merely a symbolic one."
Ronald Spogli, the U.S. ambassador to Rome, said on March 27 before the Italian Senate vote that the U.S. State Department had urged Italy to maintain its Afghan presence and to lift restrictions on its troops to allow them to engage more freely in combat.
Undermining Karzai?
But Amin Tarzi, an Afghan affairs analyst for RFE/RL, says there is an emerging debate over Italy's usefulness to NATO's Afghan mission. He says the debate is over whether Rome's handling of the hostage crisis has done damage to the NATO coalition in the country and the pro-U.S. government of Afghan President Hamid Karzai:
"The Italians demonstrated two things," Tarzi said. "One, that they are willing to negotiate with terrorists. And, two, that they are not discussing this matter with NATO; they did it on their own. And also there's a third point, which I think is crucial outside of NATO but in the long run for NATO, and that is that this act is undermining Karzai's legitimacy in establishing his prestige, in my view, in an irreparable way."
Gasparini, however, takes issue with that view.
He points out that Italy's 1,900 troops are engaged in a key stabilization and reconstruction mission in Kabul and in the area around Herat, near Afghanistan's western border with Iran. Moreover, he says Karzai himself signed off on the hostage exchange.
"The Karzai government decided to go through this way, and he [Karazi] could have rejected our positions," Gasparini said. "Yes, [Karzai's] position has been damaging [to him], but it has not been as damaging as the fact that the government does not have control of the [Helmand Province] area as such."
NATO allies raised concern on March 27 that Italy's handling of the hostage crisis could spark similar abductions of NATO troops.
Some officials called for an alliance-wide pact to ban deals with kidnappers.
"There was a clear sense in the room that none of us should agree to negotiate the release of hostages in return for terrorists," U.S. Undersecretary of State Nicholas Burns said after a NATO meeting in Brussels.
RFE/RL Afghanistan Report
SUBSCRIBE For regular news and analysis on Afghanistan by e-mail, subscribe to "RFE/RL Afghanistan Report."