BBC News - Eurozone crisis: Cameron backs euro but opposes more integration
Mr Cameron needs to hold a referendum if he wants to transfer more power from London to Brussels. The British people need to have their say.
David Cameron has said he wants the euro to succeed but insists the UK will not be part of further integration seen as "necessary" to help it continue.
Speaking in Berlin, ahead of talks with Chancellor Angela Merkel, the prime minister said the UK's "healthy growth" was linked to the eurozone's fortunes.
But he said the UK would not underwrite Spanish and Greek bank deposits or support an EU-wide financial tax.
Mrs Merkel has suggested that further political union was a pre-condition.
Mr Cameron has said the uncertainty surrounding the eurozone is the biggest threat to global prosperity and a "whole series of measures" is needed to restore market confidence in the ability of countries to pay their debts and support banking liabilities.
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Analysis
Gary O'Donoghue
Political correspondent, BBC News
David Cameron has deliberately avoided piling direct pressure on Germany to shoulder all the responsibility, saying he felt it wasn't right to single out one government.
But he has sought to keep up the pressure in other ways by saying that time was of the essence and the eurozone crisis was the single biggest threat to the world economy.
That message has been backed up by President Obama, who called both the German chancellor and the Italian prime minister the diplomatic equivalent of banging heads together.
In truth, though, the urgency of the situation is not in doubt - it's the means to resolve it where disagreement can still be found.
For example, Germany doesn't like the idea of bailing out Spanish banks directly - Spain doesn't like the idea of taking money with strings.
David Cameron will have to tread a delicate path - being outside the eurozone club he cannot dictate terms, but he's also all too aware that a quick solution is vital for stability and growth at home.
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The UK is pressing for a series of solutions, including a larger bailout fund, euro bonds and structural reform within the European Union - which could lead to greater fiscal burden-sharing between the poorest and wealthiest countries.
Mr Cameron needs to hold a referendum if he wants to transfer more power from London to Brussels. The British people need to have their say.