The euro zone will probably survive in its current form even though leaders at this week's European summit will fail to deliver a decisive solution to the debt crisis ravaging the currency bloc, a Reuters poll found.

But the poll, taken this week, was close with only a slim majority -- 33 of 57 -- saying all 17 current euro nations would continue to share the currency.

It seems pretty clear that the member countries are striving to keep it together and the implication is that they all realise that the collapse of the euro zone would be almost an apocalyptic event, said Dan McLaughlin at Bank of Ireland.

The current system has its faults ... but the alternative would be a leap into the unknown and I think most people think it would be a very messy business and they are putting sticky-back plastic here and there to keep it together.

The findings come just weeks after a separate Reuters poll of leading economists and former policymakers predicted the bloc would not survive the debt crisis intact.

European Union leaders are expected to announce on Friday their strategy to put an end to the two-year-old crisis that has spread from smaller economies on its fringes and is now threatening core euro countries, with Italy and Spain struggling to raise funds.

France and Germany, the bloc's two biggest economies, are backing a plan to amend the EU's Lisbon treaty to toughen budget discipline and overhaul the fiscal rules, boosting chances that the European Central Bank would intervene more aggressively on bond markets to calm the crisis.

But changes to the treaty face opposition from EU members outside the euro zone and countries such as Britain and Finland have threatened to block the deal unless they win safeguards protecting national interests.

Ahead of the eighth summit this year, a senior German official on Wednesday also dampened hopes for a breakthrough and said some leaders and institutions still didn't understand the seriousness of the crisis.

Two thirds of the poll respondents agreed, saying it was unlikely that the summit would put an end to the problems.

As with U.S. policymakers, we have been burned before in expecting the ultimate solution to emerge and want to see both words and actions before joining the rally. Call us more than twice bitten, and thus more than a bit shy, said Jan Loeys at JPMorgan.

The ECB, which is expected to cut interest rates and announce new support measures for banks later on Thursday, has been reluctant to buy up debt from distressed euro states more aggressively, arguing doing so would take pressure off governments to fix their finances.

But bank chief Mario Draghi has signalled that a euro zone fiscal compact could encourage the central bank to act more decisively on the crisis.

As well as cutting rates the ECB should embark on a quantitative easing programme, like the U.S. Federal Reserve and the Bank of England, where it injects money directly into the money supply to boost growth, the poll found.

The bank could also offer longer-term funding of two or three years to banks to fend off spiralling fears of a European banking meltdown.

There is a 60 percent chance the bloc will slip back into recession within the next year, a Reuters poll last month predicted.

In a further blow to nations attempting to raise funds ratings agency Standard & Poor's warned 15 of the 17 countries -- including Germany and France -- this week that it may downgrade their ratings.

S&P later said it had also put the coveted top-notch triple-A rating of the bloc's 440 billion euro (374.3 billion pound) rescue fund on negative watch, as it depends on the creditworthiness of the currency bloc's six AAA-rated sovereigns.

(Polling by Deepti Govind and Ruby Cherian; Editing by Ruth Pitchford)