Pressure is growing on eurozone leaders at the G20 summit in Mexico to find a resolution to what the head of one international organisation described as "the single biggest risk for the world economy".

A pro-euro party may have won Greece's elections at the weekend, but an announcement has yet to be made about the formation of a government in Athens, amid growing signs of impatience among other G20 nations.

World Bank chief Robert Zoellick said: "We are waiting for Europe to tell us what it's going to do."

But European Commission President Jose Manuel Barroso defended the eurozone, insisting "the challenges are not only European, they are global".

Prime Minister David Cameron has urged Greece's centre-right New Democracy party to move "decisively and swiftly" to form a new administration, warning that "delay could be deadly".

But he acknowledged that the crisis in the eurozone could rumble on "for some time" and made clear that he is looking elsewhere in the world for trading partners to replace lost demand from the UK's traditional export markets in Europe.