While both sides have tried to adopt a conciliatory tone, the threat of a disorderly default and the spread of contagion to other vulnerable countries like Portugal remains pronounced.

“In my opinion, it is unlikely that this is the last restructuring we go through in Europe,” said Hans Humes, a veteran of numerous debt restructurings and the president and chief executive of Greylock Capital, the only hedge fund on the private sector steering committee, which is taking the lead in the Greek negotiations.

“The private sector has come a long way. We hope that the other parties agree that it is more constructive to reach a voluntary agreement than the alternative.”

At the root of the dispute is a growing insistence on the part of Germany and the International Monetary Fund that as Greece’s economy continues to collapse, its debt — now about 140 percent of its gross domestic product — needs to be reduced as rapidly as possible.

Those two powerful actors — which control the purse strings for current and future Greek bailouts — have pressured Greece to adopt a more aggressive tone toward its creditors. As a result, Greece has demanded that bondholders accept not only a 50 percent loss on their new bonds but also a lower interest rate on them. That is a tough pill for investors to swallow, given the already steep losses they face, and one that would be likely to increase the cumulative haircut to between 60 and 70 percent.

The lower interest rate would help Greece by reducing the punitive amounts of interest it pays on its debt, making it easier to cut its budget deficit.

To increase Greece’s leverage, the country’s negotiators have said they could attach collective action clauses to the outstanding bonds, a step that would give them the legal right to saddle all bondholders with a loss. This would particularly be aimed at the so-called free riders — speculators who have said they will not agree to a haircut and are betting that when Greece receives its aid bundle in March, their bonds will be repaid in full.