Italian President Giorgio Napolitano will step down in hours, Prime Minister Matteo Renzi said on Tuesday, opening up a delicate political process to name a new head of state.

The 89-year-old Napolitano, who reluctantly agreed to a second term in 2013 after a deadlocked election threatened to leave Italypolitically adrift, said last month he would resign soon because of age-related ailments.

"I would like us to salute Napolitano, a committed Europeanist who in these hours will leave his post ... having confronted difficulties in Italy with intelligence and wisdom," Renzi said in a speech to the European Parliament to mark the close of the EU semester.

Napolitano had been widely expected to step down after the end of Italy's six-month presidency of the European Union, which ends on Tuesday.

Voting in parliament to name a new president is expected to begin by the end of January. A two-thirds majority of lawmakers in both the lower and upper house of parliament is needed to choose the president in the first three rounds of voting.

Hence, the selection will be an indicator of how strong a grip Renzi has over lawmakers in his ruling center-left Democratic Party.

The Italian head of state has broad political powers. He can appoint prime ministers, dissolve parliament and call early elections.

Potential candidates to succeed Napolitano include Romano Prodi, the former prime minister and European Commission president, and former Prime Minister Giuliano Amato. Both have been candidates for the presidency in the past.