Berlusconi, speaking before the start of a cabinet meeting to decide the government's response to the disaster, also pledged to immediately free 400 billion lire ($260 million) in emergency aid for the worst-hit areas.
The prime minister, facing criticism that the government had reacted slowly, said Italy faced "a disastrous situation."
"Let's put the controversies aside because the time to act is now," he said. "Later we can confront the problem of blame."
More rain fell in the northwest part of the country, much of which remained covered with floodwaters and mud -- which have caused an estimated $4 billion of damage.
Streets were littered with wrecked cars and debris swept from houses and businesses.
Hundreds of people were cut off from gas and electricity while at least a dozen communities in the worst-hit region of Piedmont were completely isolated because of blocked roads.
Pope John Paul sent his condolences to the victims in telegrams to the archbishops of Turin and nearby Asti, which was also badly affected by the floods.
Thousands of emergency service officials and volunteers continued the clean-up in Piedmont while evacuations were ordered along the banks of Po River for fear flooding could spread to the east and south.
Civil defence authorities said an estimated 8,000 people were left homeless after landslides and flooding buried scores of homes. Twenty-seven people were still missing after Piedmont's worst rainstorms for 80 years.
Local government officials estimated damage in Piedmont alone could reach $3.5 billion with another $600 million in damages in neighboring Lombardy.
Crops on half the agricultural land in Piedmont were destroyed and hundreds of factories and businesses remained closed, they said.
Some officials complained of little warning about the danger of floods despite forecasts of torrential rain.
"On Sunday afternoon, when the flood was at its height, all the TV did was advise people not to go out in their cars," said the head of Lombardy's civil protection department Alberto Di Luca.
Environmentalists blamed the catastrophe in part on soil erosion caused by widespread deforestation carried out to clear hillsides for farming, tourism and housing.
"Flooding has increased by 50 percent over the last 18 years, but the annual average rainfall has actually decreased," said the environmental pressure group Greenpeace.
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