Italian Prime Minister Silvio Berlusconi is due to begin negotiations on a new government following his resignation on Wednesday.
Mr Berlusconi said he aims to build a new administration with the parties that formed his centre-right coalition.
President Ciampi can call early elections, but he is expected to allow Mr Berlusconi to continue in office.
Mr Berlusconi's government collapsed after suffering a crushing defeat in local elections this month.
It had been the longest-serving government since World War II.
Mr Berlusconi told the upper house of parliament that his party had a mandate to lead until 2006 and it would do so.
"We have written important pages in our country's history," Mr Berlusconi said, addressing the government benches.
"With your confidence and your support, I am sure we will write many more."
"Thursday morning we will begin the consultations and they will be finished at midday Friday," he said.
Decline in popularity
Mr Berlusconi's government was plunged into crisis last week when the smallest of the four parties in the coalition, the Union of Christian Democrats, withdrew its four ministers.
His main coalition partner, the National Alliance, also threatened to quit.
It believes current policies are skewed in favour of the country's more prosperous north, represented in the coalition by the Northern League.
Correspondents say assembling a new team may prove difficult, as Mr Berlusconi risks alienating the Northern League if he gives more posts to the National Alliance.
Popular opposition to Italy's role in the war in Iraq and a struggling economy have contributed to a decline in the prime minister's popularity.
The regional elections earlier this month saw the opposition win 11 of the 13 regions up for re-election and about 54% of the vote.
(BBC)
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