WASHINGTON -- The International Monetary Fund had a sobering message for Greece this weekend: Even if the country secures debt relief from its European creditors -- a question that is by no means assured with bailout talks still deadlocked -- the nation still needs even more painful economic overhauls than currently planned.

Seven years into an economic crisis and another near-term financial emergency looming, that is a message no Greek wants to hear and a key reason why the IMF is also urging Germany and Athens' other European creditors to give the country hope in the form of real debt relief.

The country's "fiscal and structural reforms...pension reforms, tax reforms, are only a down payment," said Poul Thomsen, IMF's European department chief and Greece's original bailout architect, on the sidelines of the fund's semiannual meeting of finance ministers and central bankers.

To bring the country's unemployment and income levels back to precrisis rates will take "deep structural reforms, many of which are not yet on the books," he said. The jobless rate is currently at 22% and half of all the youth labor force are without work.

"This is a long-term project," he said.

Mr. Thomsen, along with IMF Managing Director Christine Lagarde, met with Finance Minister Euclid Tsakalotos over the weekend ahead of a return of the fund to Athens next week. Although bailout talks continue, the fund hasn't been involved in emergency financing for the country in three years, and future funding from the IMF is an open question.

Fund officials worry the Greece's existing efforts are stretching the nation's political and social limits to their breaking point. The country has already endured a series of political crises and government changeovers over the bailout years. Another could be coming, analysts say, as the government faces debt due in the coming months that it can't cover without additional help from outside creditors.

Earlier this year, the fund said the deadlock over new bailout terms, financing and debt relief risked pushing the country out of the eurozone. Analysts say Greece's crisis could be the thread that unravels the currency union, especially amid Britain's rejection of the European Union and rising anti-euro parties in key upcoming elections.

Led by powerhouse Germany, Athens' European creditors are trying to extract more economic overhauls from Greece, promising debt relief if they deliver. It is a promise that has long been offered, but not delivered, in part because Greece hasn't delivered on all its terms. Instead, Europe is trying to tweak the data to show Athens achieving a long-term budget surplus that undermines the need for debt relief.

The IMF says those projections aren't credible and is sticking to its call for Europe to give Greece real debt relief, in part trying to regain credibility it lost in the first failed bailout.

"The issue is not the targets and the credibility of the targets in the short run, but the credibility of targets being maintained over the medium-term while the economy is growing," said Mr. Thomsen. "We need a package that's credible, both in terms of the policies and in terms of the debt relief needed to improve debt sustainability."

But some economists question even whether the IMF's backing of the proposed debt-relief solutions are realistic.

Greece's public debt currently stands at around EUR326 billion, around 180% of the country's gross domestic product, EUR226 billion of which is owed to European creditors.

Jeromin Zettelmeyer, a senior fellow at the Peterson Institute for International Economics and a former top economist at the German economy ministry, doubts current proposals to extend Greece's debt maturity and cut its interest rates will be sufficient to restore the country back to health.

"Debt relief measures put on the table by the Eurogroup in May 2016 could be sufficient to restore debt sustainability, but only if these measures are taken to an extreme," he said in a recent paper. He said the private sector wouldn't accept that kind of restructuring because it gives Greece a strong incentive to default, or renegotiate, when the debt is at its peak.

"They are likely to be politically and/or technically difficult," said Mr. Zettelmeyer.

Germany, meanwhile, is facing its own election-year pressures, one of the chief reasons why Berlin isn't backing debt relief now. The government has long promised that it won't contribute any financing to Greece without the IMF's involvement because the IMF lends the program legitimacy. But since the IMF is digging in its heels on debt relief and credible bailout numbers, that is leading to another credit crunch in the coming months.

Mr. Zettelmeyer estimates, given the huge economic challenges the country faces, Greece could still require another EUR100 billion in emergency bailout cash for Greece.

Besides adding to the country's already massive debt burden, that could also deepen the budget cuts and economic overhauls required to get Athens' balance sheets back into the black and prolong what has already been a near decadelong ordeal for the country.

Write to Ian Talley at ian.talley@wsj.com