PARIS French Prime Minister Jean-Marc Ayrault sought to rally a divided left behind the European Union's fiscal compact, arguing that anything but a strong endorsement would weaken President Francois Hollande and France itself.
The Socialists have a majority in both houses of parliament, so the treaty, which ties governments to deficit-cutting plans and is a condition of further steps to resolve the euro zone debt crisis, should pass.
But the vote could be tight, with at least one coalition member - the Green party - threatening to abstain and others on the left ambivalent about the pact, which Hollande himself once opposed.
"If we want Francois Hollande - because he will be returning this week to talk to our partners - to be strong, we must keep giving him strength," Ayrault said in an interview with France Inter radio.
"The slightest sign of parliamentary weakness, which would consist in not giving him a wide majority to ratify this new stage of integration, would mean weakening France itself."
Ayrault's argument echoed words by France's European Affairs Minister Bernard Cazeneuve earlier on Sunday calling for the left to unite to push through the treaty.
"There's a need for the majority, faced with the gravity of the crisis with which we are confronted - and this is something in which all members of the majority have to play a role - to close ranks," he said in an interview with radio station Europe 1.
(Reporting By Christian Plumb and Patrick Vignal; Editing by Will Waterman)