Italian Prime Minister Romano Prodi is to offer his resignation following a major defeat in a Senate vote on foreign policy today.
Mr Prodi called a special cabinet meeting after several parties in his centre-left coalition opposed continuing with the deployment of 1,900 troops in Afghanistan and plans to expand a US airbase in Vicenza in northern Italy.
"Prodi is going to hand in his resignation to the Quirinale [president's palace]," Mr Di Pietro said.
President Giorgio Napolitano cut short a trip to Bologna to return to Rome for talks with Mr Prodi.
As right-wing senators called for Mr Prodi to step down, Mr Napolitano considered whether to accept the resignation of a prime minister who took power just nine months ago.
Dissolving parliament and calling an election is an option but Mr Napolitano could ask Mr Prodi to test his majority with a vote of confidence - a move supported by Justice Minister Clement Clemente Mastella.
The President could also ask him to form a new government or attempt to broker the formation of a new coalition government.
The Senate vote was not binding, but Foreign Minister Massimo D'Alema said earlier the government should resign if it lost the vote. Some 160 votes were needed motion but with 24 abstentions it only managed 158.
The announcement of the result in the upper house was met by shouts of "resign" by right-wing senators. The sitting was suspended shortly afterwards.
Former prime minister Silvio Berlusconi was among the opposition forces clamouring for Mr Prodi to step down.
"Foreign police involves the role and image of Italy in the world and the life of our soldiers committed to international peace mission," he said.
Tens of thousands protested in Vicenza last week against expansion of the US base as agreed by Mr Belusconi. Mr D'Alema had said the government was compelled to allow it go ahead otherwise the Washington would regard it as "a hostile act".
Communist and Green Party members of the so-called Catholics-to-Communists coalition oppose continuing with a presence in Afghanistan
The motion asked the senate to approve the government's foreing policy, which it said was inspired by a repudiation of war and respect for the role of the EU, UN and international alliances.
The defeat was the most serious setback for Mr Prodi's coalition, also deeply divided over domestic issues ranging from the budget, pension reform and a bill giving legal recognition to gay and unwed couples.
Agencies