The biggest banks in the eurozone met Wednesday to hash out ways to contribute to any new financial rescue package for Greece, as trouble in Portugal revived worries about Europe's financial health and hit stock markets in Spain and Italy.
The meeting of senior executives from top European banks in Paris ended with no public announcement of a deal, but plans for further discussions in the weeks ahead.
European governments are trying to seal a new bailout package for Greece by September to help the government pay its bills and avoid a default whose effects could ripple worldwide.
Even before a new package is in place, concerns about Greece could cause investors to pull money out of other vulnerable eurozone states, such as already bailed-out Portugal and Ireland as well as much larger Spain and Italy.
Portugal's financial plight deepened Wednesday as the interest it pays on loans jumped higher and its stock market slumped, a day after its government bonds were downgraded to junk status. Stocks fell all round Europe, but especially in Spain and Italy too.
The bankers' private talks in Paris, under the auspices of the Institute of International Finance, ended in the early afternoon, spokesman Frank Vogl said, without revealing what if anything was decided.
"This was seen as part of a series of meetings and there will of course be further meetings," he said.
The bankers' main task is to come up with terms under which they would be prepared to buy up new Greek bonds, currently seen as one of the riskiest investments in the world.
The IIF said in a statement last week that the bankers would discuss a voluntary rollover of Greek bonds, and that the goal is to provide "significant cash-flow support to Greece during 2012-14 on the basis of broad-based voluntary participation by private investors."
Eurozone governments want substantial private-sector contributions to a new rescue deal for Greece, so the whole burden doesn't fall on taxpayers, many of whom are angry at having to bail out a country long seen as sloppy with its finances.
German Finance Minister Wolfgang Schaeuble insisted Wednesday that the private sector will have to play a central role in the new Greek aid package and noted that Europe's biggest economy was prepared to work on the basis of a recent proposal from French banks.
Under the French proposal, banks would reinvest 50 percent of their holdings in new Greek bonds with a maturity of up to 30 years and being secured by a separate safety fund.
Schaeuble added that "there are also a lot of arguments for alternatives, and we will have to discuss that calmly but thoroughly by September." He didn't elaborate.
France's new Finance Minister Francois Baroin said Wednesday that a plan worth somewhere in the region of euro100 billion ($144.6 billion) should be ready for September.
Baroin said he will go to Berlin on Thursday for talks with Schaeuble.
The European Commission has said that Greece will need an extra euro115 billion ($166 billion) through the middle of 2014, on top of the euro110 billion ($159 billion) from European governments and the International Monetary Fund granted a year ago _ although some of that financing will come from the sale of public assets and the private-sector contribution.
Eurozone governments are keen to make sure that any rollover of Greek debt by the banks is not considered a default by credit rating agencies. No eurozone country has ever been considered to be in default of its debt, and the European Central bank fears that such a negative rating could undermine investor confidence in banks throughout the currency union.
Though last week's decision by the Greek Parliament to back further austerity measures in return for crucial bailout funds has helped calm jitters in the markets, Europe's debt crisis is likely to remain a major concern for investors.
The decision by Moody's to downgrade Portugal to junk status late Tuesday weighed on European stocks and the euro Wednesday. The agency said the country will find it difficult to meet its targets and that it too may need a second bailout.
In Greece, strike action remains a major obstacle to the government's program. On Wednesday, taxis across Greece are holding a 24-hour strike to protest the opening of their profession to more competition.
Geir Moulson in Berlin and Gabriele Steinhauser in Brussels contributed to this report.