ATHENS — Greece’s place in Europe once again hung in the balance on Friday, as the fragile interim coalition of Prime Minister Lucas Papademos was plunged into turmoil and European leaders expressed doubts about the country’s commitment to remaking its economy and achieving solvency.

After a wave of defections from his cabinet, and as protests turned violent in Athens amid a general strike, Mr. Papademos told lawmakers that they must approve new austerity measures demanded by Greece’s creditors — including a 22 percent cut in the benchmark minimum wage and public-sector layoffs — or the country would suffer a disorderly default with social dislocation and would eventually leave the euro zone.

After a five-hour meeting, the cabinet approved the package, sending it on to Parliament for final approval, perhaps as early as Sunday.

The prime minister’s comments kicked off what is expected to be a long and chaotic weekend of brinkmanship, with Greek politicians fighting for their survival in the face of unpopular austerity measures and European leaders demanding more concessions in a climate of growing urgency — and mistrust — between Greece and its foreign lenders.