PARIS — Global stocks rose on Tuesday, even as the Organization for Economic Cooperation and Development cut its growth forecast for the euro zone and said Europe risked creating a self-sustaining cycle of decline that could have dire effects for the world economy.


Pier Carlo Padoan, the O.E.C.D.’s chief economist, warned that Europe risked creating “a vicious circle, involving high and rising sovereign indebtedness, weak banking systems, excessive fiscal consolidation and lower growth.”


Such an eventuality would be felt beyond Europe’s borders, “with very serious consequences for the global economy,” Mr. Padoan wrote in an O.E.C.D. economic report.


“The crisis in the euro zone remains the single biggest downside risk facing the global outlook,” he said.


The O.E.C.D. estimated that growth in the 17-nation euro zone would shrink by 0.1 percent this year, worse than that 0.2 percent growth it had previously forecast. The organization also cut its forecast for 2013 growth to 0.9 percent from its previous estimate of 1.4 percent.


The euro crisis began more than two years ago with revelations that government finances in a number of countries in the 17-nation currency zone were worse than thought, in some cases because governments had rescued financial institutions damaged in the 2008 market meltdown. After bailouts for countries including Greece, Ireland and Portugal, and concern that Spain and Italy might also ultimately need help, there are now fears about the survival of the euro itself.


On Monday, President Barack Obama expressed confidence that European leaders were buckling down to solve the crisis, and he called for concrete steps to ensure any fallout from the crisis is contained.


“We’ve got to put in place firewalls that ensure that countries outside of Greece that are doing the right thing aren’t harmed just because markets are skittish and nervous,” Reuters quoted Mr. Obama as telling a news conference in Chicago.


“We’ve got to make sure that banks are recapitalized in Europe so that investors have confidence,” Reuters quoted Mr. Obama as saying. “And we’ve got to make sure that there is a growth strategy to go alongside the need for fiscal discipline, as well as a monetary policy that is promoting the capacity of countries like a Spain or an Italy to put in place very tough targets and some very tough policies.”


The warnings for Europe comes as François Hollande, the French president, prepares to make the case for joint euro zone bonds when European Union leaders meet Wednesday for an informal summit in Brussels. Mr. Hollande has allies among the struggling nations of the euro zone periphery.


Chancellor Angela Merkel of Germany has long championed a tough fiscal pact limiting governments’ room to maneuver as the way out of the crisis. While Mrs. Merkel has lately shown more willingness to entertain a mixed growth and austerity agenda, she is not alone in viewing the idea of euro bonds with skepticism.


The Austrian finance minister, Maria Fekter, derided the idea of joint euro bonds as “nonsense” in an interview with the Oberösterreichische Nachrichten newspaper.


It is not yet clear just how ambitious Mr. Hollande’s plans for joint bond issuance are. Some officials and commentators have suggested that euro zone governments could go so far as to issue bonds guaranteed by all euro members, something that would allow the currency union’s struggling members to finance their government budgets at far cheaper rates than currently.


More modestly, the European Investment Bank could issue jointly backed “project bonds” to fund infrastructure development in euro zone countries, an idea that has been widely applauded.


Holger Schmieding, chief economist at Berenberg Bank in London, said Germany would never agree to broadly pool its finances with the rest of the euro zone, in effect guaranteeing the budget spending of Italy and other countries.


“Forget that idea,” he said. “I don’t think it’s going to fly. But there are many other ways to contain contagion from Greece without euro bonds. It’s not a choice between the end of the euro and issuing euro bonds.”


Mr. Schmieding pointed to the European Financial Stability Facility, the zone’s main bailout vehicle, which is supposed to be superseded by a permanent fund, the European Stability Mechanism, on July 1. If need be, he said, euro nations could add firepower to those facilities.