"I will push for necessary treaty changes so that we can act sooner and more effectively when things go wrong, including with targeted sanctions," she said.

Euro under threat

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Spain, which holds the rotating presidency of the EU, has said a "European solution" is needed to help Greece, which needs for borrow around $21.4bn between April 20 and May 23 to refinance maturing debt.

Greece says it needs only a standby aid package to reassure nervous financial markets and that it can get by without having to resort to using the money that is set aside for it.

But Germany, Europe's biggest economy, faces public opposition to any bailout for Greece before a regional election in May and fears any financial assistance would face a legal challenge at home.

Greece has already taken a string of austerity measures, prompting widespread and largescale domestic strikes and protests.

EU leaders are concerned debt-servicing problems could also hit other countries in the euro zone including Portugal, Spain or Italy.

Wrangling over the Greek issue has also threatened cohesion across the eurozone and driven down the value of the euro currency, used by 16 member states including Greece.

On Wednesday, the euro fell more than one per cent against the dollar on to $1.3335, its lowest since May 2009, and continued heading down on Thursday.