A summit of European Union leaders to thrash out a master plan to fix the eurozone debt crisis opened in Brussels on Wednesday.

The gathering of EU presidents and prime ministers is their second summit in days as markets and world leaders call on them for a watertight deal to prevent the festering crisis from sparking a global recession.

The talks are to be followed by a summit later Wednesday of the 17 EU members that share the euro which could last well into the night.

Going into a series of pre-summit meetings, leaders indicated that a wide-ranging plan was not yet ready.

German Chancellor Angela Merkel said "there are still many problems to settle and negotiations to carry out, so the work is not yet over."

Acknowledging the summit could fall short of expectations, Luxembourg Prime Minister Jean-Claude Juncker said: "We will likely not set out everything in the finest details, but the general direction" that must be taken.

Europe's leaders have been scrambling to produce a plan to shield the euro after two years of turmoil embroiling Greece, Ireland and Portugal and now threatening the eurozone's third and fourth economies, Italy and Spain.

Tighter eurozone fiscal discipline is one element in a package that includes beefing up a rescue fund to guard against further contagion, agreeing a massive write-off for banks on Greek government debt, and recapitalising Europe's banks so they can absorb the hit.