Andrew Higgins writes:  To many Greeks, the debt the country has amassed is the evil fruit of austerity policies, imposed from the outside, that asphyxiated its economy and trampled on its sovereignty.

To the International Monetary Fund, the debt of more than 310 billion euros, or almost $339 billion, is more of a mathematical problem. After years in which it was a stern advocate of tough austerity policies, it now says that there is no way that Greece can reasonably pay its debts and needs to have a substantial amount of it forgiven.

Then there is Germany, Greece’s largest single creditor, which treats Greece’s debts as a sacrosanct commitment that must be paid as a matter of law and of principle.

Mr. Tsipras has for years been demanding a European Debt Conference modeled on the London Debt Agreement of 1953 that wrote off about half the pre- and postwar debt taken on by West Germany.

Persuading creditors to accept losses has never been easy or free of a political component. The London conference negotiations dragged on for two years and involved representatives of public and private creditors from 26 countries.

But the United States, Berlin’s biggest public creditor, pushed through the deal, largely out of strategic concerns heightened by the Cold War.

The Greeks, by contrast, “are just not important or powerful enough to make everyone want to rescue them,” said Timothy W. Guinnane, a professor of economic history at Yale University who has studied the 1953 London negotiations.

The contentious negotiations this month that produced the framework agreement for the new bailout of Greece offered only a vague pledge to consider the possibility of “longer grace and payment periods” on the condition that Greece first meets its own commitments to tightly control spending.

Chancellor Merkel, who continues to rule out debt forgiveness, said on Sunday that Germany would entertain a discussion about steps such as lower interest rates and longer payment terms, but only after the bailout agreement is finalized and Greece passes a first assessment of its progress in carrying out the policy changes demanded by the creditors.

Christine Lagarde, the managing director of the I.M.F., told a French radio station last week that the new Greek bailout now taking shape is “categorically not” viable without debt relief.

A big reason for the standoff is the nature of Greek debt. In many previous international negotiations — including those over money owed by Latin American countries during the region’s debt crisis in the 1980s and the €107 billion in debt that Greece got written off in 2012 — the creditors were mostly foreign banks and other investors.

When Germany and other eurozone nations fashioned their first bailout to Greece in 2010, they offered a package of bilateral loans, an approach that, according to Mr. Dallara, the American debt negotiator, “introduced an unusual level of politicization into debt negotiations.”

Germany’s contribution to the two initial bailouts was more than €50 billion, making Berlin the biggest contributor. But some experts believe that once German contributions to the European Central Bank and to other lenders are taken into account, Berlin is on the hook in Greece for upward of €100 billion.