Other European government bond yields were also lower, but the drop was more moderate, with peripheral countries roughly in line with the core, tracking U.S. Treasuries.
One possible scenario if Italia Viva quits would be for all the coalition parties to renegotiate a new pact, which would almost certainly open the way for a major cabinet reshuffle, with or without Conte at the helm.
The coalition collapsed a year later, but he stayed on at the head of a left-leaning government cobbled together between the M5S, PD and smaller allies.
Italy has been highly supportive of Britain since the country voted to leave the EU bloc and has consistently stressed the need for all sides to make compromises to secure a deal.
Atlantia, controlled by the powerful Benetton family, agreed in July to pull out of Autostrade following the 2018 collapse of a motorway bridge run by the unit.
Conte said discussions were in the "final straight", without giving further details.