The seven-party talks have dragged on for nearly three months since Flemish nationalists, the New Flemish Alliance (N-VA), triumphed in Flanders in the June legislative elections.
"The parties that refuse a balanced compromise will plunge our country into the unknown, or even political chaos," Di Rupo told a press conference.
The main stumbling blocks include the future of francophone suburbs of Brussels that lie within Dutch-speaking Flanders, the refinancing of the national capital region and a new federal financing law.
Di Rupo, whose Socialist party came out on top in the French-speaking Wallonia region in June, said he hoped that "reason will finally prevail."
Should Di Rupo succeed in forming a government, he would be Belgium’s first francophone head of government since Paul Vanden Boeynants, a Brussels Christian Democrat who was prime minister from October 1978 to April 1979.
A country of 10.5 million people, 60 percent Flemish, Belgium already has heavily devolved regional governments, divided along linguistic lines.
AFP/Expatica