Europe Union finance ministers remained divided on Tuesday over what data would be published in banks stress tests due in 10 days but pledged to make them as transparent as possible.

Like U.S. tests announced in May last year, they are intended to identify which banks need to raise new capital and to restore confidence shaken by the euro zone's recent debt woes.

Belgian Finance Minister Didier Reynders, whose country holds the rotating presidency of the 27-nation EU, played down reported differences over what data should be made public.

We have taken an agreement...about the need to devote to transparency, Reynders told a news conference after a monthly meeting of the finance ministers.

There is no problem about the choice ...It's only a problem of coordination, to be sure that we are publishing at the same moment...all the figures, Reynders said.

But ministers said divisions remained over the process.

We are still discussing what we are going to publish from the stress tests, Swedish Finance Minister Anders Borg told reporters.

The plan is to announce on July 23 how banks would fare if economic conditions turned worse, including a deeper fall in the value of sovereign bonds.

The tests will apply, for example, a 23 percent discount on Greek sovereign debt held in banks' trading books, a banking source told Reuters on Tuesday.

But there have been splits in the 27-nation EU over how to model such scenarios and how much to publish once the results are in from questionnaires sent out to banks last week.

French Economy Minister Christine Lagarde said a final decision might have to wait until a teleconference of EU finance ministers set for July 22. Discussions will continue until the last minute, she said.

France was questioning the need to publish the exposure of banks to sovereign debt and underlined the difficulties of having a harmonized tier one capital ratio which would enable comparisons across the EU, sources said.

Germany supported publishing the banks' sovereign debt exposure while Britain and Spain were pushing for full transparency, the sources said.

Stephen Hester, chief executive of Royal Bank of Scotland supported openness.

Most things to increase transparency in financial markets I'm in favor of, he said at a British Bankers' Association conference in London.

The tests cover 91 EU banks accounting for 65 percent of the bloc's banking sector. Along with the biggest, the list includes many German and Spanish regional banks, thought to be among the weakest.

Doubts about European banks' ability to clean up their balance sheets have limited their ability to raise funding and made them highly dependent on the massive liquidity taps which the European Central Bank opened after Lehman Brothers collapsed in 2008.

There is still too much turmoil on the markets, partly because there are still uncertainties over the that is why transparency is better, German Finance Minister Wolfgang Schaeuble told reporters.

Credit Suisse analysts last week estimated the tests will indicate European banks need to raise up to 90 billion euros including 37 billion euros for Germany's regional banks and 12 billion for Spain's savings banks.

Bank analysts have estimated that up to 20 lenders might be directed to raise capital.

Following the U.S. tests last year, several of the 10 found short of capital swiftly announced fundraising plans of their own, steering clear of state aid.

Bank of America Inc , which had the largest shortfall at $33.9 billion, announced it would issue $17 billion in common stock, sell assets and take other steps, for example.

Europe's banks might raise their own funds, tap national funds set up in countries such as Germany and Spain, or a 60 billion euro EU fund. If that is not enough, they could turn to the 440 billion euro European Financial Stability Facility organized in early May at the height of the euro zone's debt crisis.

Olli Rehn, the EU's commissioner of economic and monetary affairs, said banks should try to recapitalize themselves by tapping private investors and that public money should be used only as a last resort.

Nevertheless, in case any elements of vulnerability are identified, systems are in place to deal with them swiftly and properly, he said.

The tests are managed by the London-based Committee of European Banking Supervisors (CEBS), which last week published two basic assumptions -- economic growth falling 3 percent below official forecasts for this year and next and a shock to government bonds similar to the situation observed in early May. No precise figures for that were given.

This test has some very tough assumptions including another economic slump which in reality we do not see happening at all, ECB Governing Council member Ewald Nowotny told Austrian broadcaster ORF.

Belgium's Reynders said test results would be published in two stages, with those for some subsidiaries of large banking groups coming about two weeks later.

(Reporting by Ecofin team in Brussels and Steve Slater, writing by Jan Strupczewski, Editing by Ruth Pitchford, Jason Neely)