European leaders jetting off to Mexico for a G20 summit dominated by the eurozone crisis will stage a preparatory conference on Friday afternoon, an EU spokesman said.

"There will be a video conference call with the leaders of those European countries taking part in the G20 talks," France, Germany, Italy and non-euro Britain, said the spokesman for European Union president Herman Van Rompuy.

The conference call, which is to begin at 1400 GMT, will also feature Van Rompuy and European Commission head Jose Manuel Barroso and is meant to serve as "a coordination meeting" before Mexico, where the G20 is to meet on Monday.

The EU collectively holds a seat in the grouping of 20 major global economies along with leading EU members.

Similar preparatory talks are held before talks by the G8 group of highly industrialised economies, the spokesman, Dirk De Backer, underlined.

The eurozone in full crisis-prevention mode ahead of Sunday's general election in Greece, owing to the potential risk that Athens could end up exiting the 17-nation bloc.

An agreement to lend Spain up to 100 billion euros ($126 billion) to recapitalise its banks, awaiting a formal request from Madrid expected next Thursday, has failed to calm markets, causing unease over Italy's prospects too.

Market sentiment has improved somewhat however, with some betting that Greek voters will back a governing coalition that can stick to the terms of a March deal for the country's 237-billion-euro second bailout.

The terms include more deep budget cuts and economic reforms.

Ahead of the talks, German Chancellor Angela Merkel lamented on Friday a "lack of confidence" among eurozone leaders as it plots the way forward.