But policy makers and analysts were quick to caution that the Fed’s action did not address the fundamental financial problems threatening the survival of the European currency union. At best, they said, efforts by central banks to ease financial conditions could allow the 17 European Union countries that use the euro sufficient time to agree on a plan for its preservation.

“The European sovereign debt problem will not be solved only with liquidity,” the governor of Japan’s central bank, Masaaki Shirakawa, told reporters in Tokyo. He said that he “strongly” expected Europe to “push through economic and fiscal reform.”

European leaders, increasingly concerned by a deteriorating financial picture, said Wednesday they were forming a plan to convince markets that the debts of nations like Italy and Greece were not overwhelmingly large and to set new rules to constrain borrowing by euro zone members. They pointed to a scheduled meeting in Brussels on December 8-9 as a looming deadline for those efforts.

“We are now entering the critical period of 10 days to complete and conclude the crisis response of the European Union,” Olli Rehn, European commissioner for economic and monetary affairs, said Wednesday after a meeting of European finance ministers.