Greece could default on its debts and possibly exit from the euro currency zone if the country can’t make convincing progress in the next few weeks on long-promised economic reforms, Prime Minister Lucas Papademos told national business and union leaders in Athens on Wednesday.

Negotiations over how to stabilize Greece’s finances remain unresolved on several fronts, and the fallout from a default by the country — or its exit from the euro zone — would be unpredictable and potentially traumatic for the European economy.

Greek officials are negotiating a restructuring of about $200 billion in privately held debt with finance industry leaders representing the banks, pension fund managers and other investors who hold the bulk of the outstanding bonds.

The aim is to reduce the amount that Greece owes by $100 billion and ease its debt load. While negotiators say progress is being made, a detailed agreement has eluded them despite several weeks of on-and-off discussions.

European Union and International Monetary Fund officials, meanwhile, will begin talks later this month about a new and expanded international bailout designed to carry Greece for at least three more years. That could give the country more time to rekindle economic growth and overhaul government finances.

Both sets of talks hinge on Greece living up to a set of commitments involving changes in wages, labor rules and other practices aimed at making the country more competitive with its European neighbors. Papademos said that Greece faces a “disorderly default” when a major bond payment comes due in March if the government is seen as stalling on those changes and talks with the banks or international lenders break down.

“If we do not make the necessary adjustments, it is to be taken for granted that we cannot expect that the other E.U. countries and international organizations will continue to finance a country that does not adjust to reality and does not tackle its problems,” he said, according to a transcript of his remarks released by his office and reported by news services in Athens.

Papademos took office in November as head of a national unity government assembled to carry out the country’s commitment to overhauling its economy, but he has struggled.

Union leaders left Wednesday’s meeting saying they would oppose the concessions being demanded by Greece’s international lenders on wages and other matters. Greek wages are considered by European analysts to be far higher than those in the rest of the region, and Greece’s expensive public payroll has contributed to an unsustainable level of government debt.

Major international lenders agreed in October to reduce the face value of Greece’s outstanding debts by 50 percent and began talks over what is envisioned as a voluntary swap of existing bonds for new bonds worth half as much.

But translating that agreement into a detailed deal has proved difficult amid disagreement over the interest rate and duration of the new bonds.

In addition, while major investors have promised to participate in hopes of avoiding a full Greek default, they also have an incentive to hold out. To date, using money loaned by European nations and the IMF, Greece continues to make good on its bond obligations, and as recently as Dec. 29 it paid off a maturing bond worth around $6.5 billion to the investors who held shares in it.

The bond maturing in March is much larger, around $19 billion. Greek officials said this week that they may have no choice but to default if the debt restructuring and new international loans are not in place by then.