Italian Prime Minister Enrico Letta announced his resignation after his own party yanked away vital support for the government, with Democratic Party leader Matteo Renzi now expected to replace him.
Letta said he will submit his resignation to President Giorgio Napolitano on Friday.
Florence Mayor Renzi told fellow party leaders yesterday that it was time for "radical change" in economically stagnant and politically unstable Italy as he looked for a mandate to shepherd electoral and other economic reforms through parliament.
"Italy cannot live in a situation of uncertainty and instability. We are at a crossroads," Renzi, widely expected to take over if Letta steps down, told the 140-strong leadership committee, calling for a radical reform programme.
After growing criticism over the slow pace of economic reform, Letta, a low-key moderate appointed to lead the cross-party coalition patched together after last year's deadlocked elections, has been increasingly isolated.
Renzi acknowledged that forcing Letta to go and trying to form a new government with the centrist and centre-right parties that backed his coalition carried risks for both the government and himself personally, but said there was no alternative.
"Putting oneself on the line right now carries an element of risk, but a politician has the duty to take risks at certain moments," he said.
He said it would be impossible to hold new elections while the current voting law, which was blamed for the stalemate after last year's election, remained in place.
But Letta earlier dug in his heels in the face of an increasingly formidable threat.
Letta said it was "not in [his] DNA" to break with the agenda of his government and challenged Italy's political players - chiefly Renzi - to "lay their cards on the table".
Less than 10 months after it was born from the inconclusive mess of last February's general elections, long-running criticism of the coalition government's lacklustre record gathered force, putting Renzi, the 39-year-old mayor of Florence, in a leading position to take over as prime minister in an election-free process branded by the media as la staffetta - the relay.
Ever since he won the primary leadership election by a landslide in December, Renzi - a politician viewed as refreshingly energetic by his supporters and insufferably brash by his critics - has kept up regular attacks on Letta's government from the sidelines, pointing out its failings and urging it to do more, particularly focusing his energies on pushing through a new electoral law.
But, until recently, the idea of taking over from his colleague without first going to the polls is not understood to have been considered a viable option.
Were he to take over the reins, he would become Italy's third unelected prime minister in under three years, after Mario Monti was brought in to head a technocratic government at the end of 2011 and Letta was put in charge of his awkward coalition with Silvio Berlusconi's centre-right party last April.
According to opinion polls, it is not a move many Italians support, despite their approval of Renzi himself.
Reuters, Associated Press, The Guardian