Renzi, who quit as premier after losing a December referendum but still leads the PD, secured the backing of the party's executive for an assembly that will set a date for the leadership vote.

"We are coming to the end of a cycle," Renzi told fellow party heavyweights, confirming he would again be a candidate to lead the party into elections that must take place by next February.

Renzi is reported to favour a June date for an election which will see his party go head to head with the populist Five Star Movement, which is running the PD close in the opinion polls.

But he insisted on Monday that he did not think it was up to him when the election was held.

Renzi stepped down as premier after his constitutional reform proposals were overwhelmingly rejected. But he made it clear he planned to return and was widely seen as having hand-picked his successor, Paolo Gentiloni, as a stand-in who would pose no long-term threat to that.

Five Star also backs an early election but lawmakers must first agree on a new electoral law, a task which many feel will delay the vote until the autumn at least.