Renzi, 39, is considered likely to be given a mandate from President Giorgio Napolitano when he is formally installed in office this week; however, PD leader Angelino Alfano said Renzi should not think that means he can ride roughshod over his allies.
"We are decisive for the creation of the new government," Alfano said at a meeting of New Center Right, which was a key backer of Renzi in his campaign to replace outgoing Premier Enrico Letta. "If we say no to this government, it won't come to life."
Italy's ANSA news agency said Alfano, who is also deputy premier and Italy's interior minister, is keen on maintaining his posts and also wants to preserve the four Cabinet seats the NCD holds.
Britain's Financial Times said Alfano's stance had reportedly caused the 88-year-old Napolitano to have second thoughts about handing Renzi a mandate without further consultations.