Italian Prime Minister Romano Prodi resigned Wednesday after his ruling centre-left coalition suffered a major defeat in a Senate vote.

Prodi's government, which came to power less than a year ago, failed to gain majority support of a motion backing its foreign policy. The coalition is deeply divided over issues such as the war in Afghanistan and ties with the U.S. military, as well as over domestic issues such as the budget.

Italy has 1,800 troops in Afghanistan, which were sent in by former prime minister Silvio Berlusconi. The current government has agreed to keep the troops there, sparking opposition from its own Communist allies.

The defeat prompted Prodi to submit his resignation to President Giorgio Napolitano, Prodi's aides said.

Napolitano's office said consultations to see who had the support to put together a new government would begin Thursday.

In the meantime, Napolitano asked the government to stay on in a caretaker role, his office said.

In the Senate, right-wing opposition members chanted "quit, quit, quit" following the vote, which fell two votes shy of the necessary majority of 160. Twenty-four senators abstained.

More than 100 opposition supporters gathered outside Prodi's offices calling for him to step down as he met with his cabinet, the BBC reported.

Several options for president 

Prodi was under no constitutional requirement to resign after the vote, but decided to step down. According to Italian law, it is now up to the president to decide whether to accept Prodi's resignation or call on the prime minister to hold a confidence vote or form a new government.

Napolitano can also take a radical step and call an election.

Italian politics are renowned for frequent collapses of coalition governments. Since the end of the Second World War, no single party has won enough seats to control the Chamber of Deputies or the Senate, the two houses that make up the Italian Parliament.

Prodi came to power last April in a narrow victory over the previous centre-right coalition government, led by Berlusconi, who conceded defeat more than a month after the election following a lengthy court battle over the result.

With files from the Associated Press