If Greece goes out, the euro might break down, warned Greece's chief debt negotiator.

A Greek exit from the euro might prompt its own demise, the country's chief negotiator has warned.

"If Greece goes out, the euro might break down," said Euclid Tsakalotos.

"Once one country has left, you change a monetary union into a fixed exchange rate system, where it's a cost-benefit analysis whether another country leaves."

He told the Today programme: "My greatest fear is that the break-up of the euro will return (us) to the competitive devaluations, and the nationalisms, and the kind of politics we had in the 1930s."

Any deal had to be one that was economically feasible, he told Today, as the country must be able to keep its fiscal promises.

"We have been in a compromising mood, we've been suggesting ideas, whereas the institutions presented a paper that was very close to their original bid.

"So what we are saying is that further compromises can be made, we can search for common ground, but the end product of what we agree on reforms, on the financing for the future, on the investment programme must be economically feasible."

Earlier, Mr Tsakalotos had warned that without help, Greece would be unable to meet its obligations to the IMF on 30 June.