In his second day in Rome, Karzai bitterly condemned the havoc that the Taliban wreaked on Afghanistan and said he would hand over Arab guerrillas caught in his country to face international justice.
He also urged the international community on Wednesday to remain engaged after the war on terrorism ends.
"The international community saw the consequences of neglecting Afghanistan," Karzai told a press conference.
He said he didn't know where Osama bin Laden or Taliban leader Mullah Mohammed Omar were, but said terrorists and their supporters would not be welcome in the new Afghanistan.
"There's no way we can allow them to stay. They've killed our people, they have destroyed our land. We will finish them to the end," Karzai said.
"The Arabs in Afghanistan who have no criminal record are just citizens...but the ones who have committed international crimes, crimes against mankind, crimes against our people, they must face international justice," he told a news conference.
He said he envisioned an international peacekeeping force of about 3,000 to 5,000 troops that would be authorized to use force not only in self-defense, but to keep the peace.
"If it takes the use of force to keep the peace, why not?" he said.
Asked what he would do with bin Laden, the Islamic militant Washington holds responsible for the Sept. 11 attack on the United States, Karzai said:
"If I knew (where he is) I would arrest him straight away."
Karzai added that bin Laden also would be handed over to international justice if he were caught.
"It's an international issue, terrorism. A man like that who has committed crimes worldwide must be given to international justice," he said.
He spoke to reporters after getting the blessings of Afghanistan's former king. He is set to take office on Saturday as the head of an interim government that will rule Afghanistan following the ouster of the Taliban.
On Wednesday, the second day of his visit to Rome, Karzai also met with the U.S. ambassador to Italy.
U.S. Ambassador Mel Sembler "was interested in hearing from Karzai on the situation" in Afghanistan, said embassy spokesman Ian Kelly. "We had no particular message to deliver."
Karzai paid his respects to Mohammad Zaher Shah at the exiled monarch's Roman villa on Tuesday evening and said there that his top priorities in office would be to "fight terrorism to the end" and revive Afghanistan's war-wrecked economy.
As if to underscore the importance of the moment, Zaher Shah stepped outside the heavily guarded home to make a rare appearance before media. Zaher Shah said he had given Karzai advice on "a lot of things" on how to lead the country, but didn't elaborate.
"He has been giving me advice for many years," said Karzai, a distant relative of the king's and also Pashtun, Afghanistan's dominant ethnic group. "The moment I sat with him, he wisheme very very well and said he was very very glad that I have taken this charge."
The 87-year-old king, considered the symbolic father of Afghans, presented Karzai with a personal copy of the Quran, encased in a green, leather-bound box, which Karzai said would guide him once he takes office on Saturday.
Karzai kissed the holy book, as well as the king's hands, in thanks.
"This gives me tremendous hope, tremendous hope, that under the guidance of the Holy Quran and his majesty's blessings, I'm going back home," Karzai said.
The encounter capped a day in which Karzai received a pledge from Italian Premier Silvio Berlusconi for $38 million in government aid, a promise from the media magnate-politician to fund a TV and a radio station and a minute of applause from lawmakers in the Chamber of Deputies.
Italy has offered up to 600 troops for an international peacekeeping force in Afghanistan that is to help keep the peace following the ouster of the hard-line Taliban rulers. The first units of the force, expected to be led by the British, could be on the ground by Saturday's swearing-in ceremony.
Karzai said the peacekeepers would be welcome to stay "as long as it takes for Afghan stability," but offered no details on what he would like to see them do. He said the creation of an Afghan national army was key to preventing Afghanistan's warlords from undermining security.
Once peace is restored, he said his priorities in Afghanistan were to "arrange for our children to go to school as soon as possible and to provide the Afghan people with a fair chance to engage in economic activity and to live a better life."
Karzai was selected to head Afghanistan's interim administration at U.N.-sponsored talks in Germany earlier this month. Karzai, who was part of the king's delegation, will rule along with a 29-member cabinet for six months.
The king, seen by many as a unifying figure, is to then convene a grand national assembly, or loya jirga, which would choose a government to lead Afghanistan for two years while a constitution is drafted and a judicial system and police force are put into place.
The king, who has lived in Rome since his 1973 ouster, could depart for the country to start making plans for the tribal assembly within the next month or two, said an adviser, Zalmai Rassoul.
Rassoul and another adviser, Rehim Sherzoi, were to return to Kabul with Karzai to represent the king at Saturday's swearing-in ceremony.
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