The Italian President, Giorgio Napolitano, has begun talks with political leaders following yesterday's sudden resignation of the Prime Minister, Romano Prodi, whose government has been in office for only nine months.
Mr Prodi's departure followed a defeat in the Senate over his plans to dispatch troops to Afghanistan and allow the expansion of a US airbase in the northern Italian town of Vicenza.
Fresh elections may be called if there is no agreement of forming a new coalition government.
Mr Prodi had led a nine-party coalition after defeating Silvio Berlusconi in Italy's most closely contested election in post-war history last April.
Under the Italian constitution, President Napolitano must find a way out of the impasse.
The main options include another Prodi-led administration, a caretaker government of experts with cross-party backing or fresh elections.
Left revolt
The Afghanistan deployment and the enlargement of the US base were both strongly opposed by the Greens and Communists who made up part of the coalition which also includes liberal and Catholic parties.
More than 80,000 people took part in a rally last Saturday in Vicenza against the base enlargement.
The government needed 160 votes in the Senate debate to get a formal motion of support. But only 158 senators voted in favour and 136 opposed the government.
Until last April's election, Italy's left had been in the political wilderness for five years while Silvio Berlusconi maintained a pro-US foreign policy.
Mr Prodi had accelerated the withdrawal of troops from Iraq, but angered left leaning politicians for not ending Italy's participation in the Afghanistan peacekeeping mission.
