When a central bank (or World Bank) has the power to create a country's money and lend it to that country's circulation, it is mathematically impossible to pay the interest since only the principal was ever created.

Even the principal can't be repaid because much of it has been saved by little people and put into nest-eggs. Bankers don't accept turnips and dancing lessons as payment, only the same cash that they themselves created.

If that country trades at a profit, the next country is obviously going to lose and you create so-called "developing" countries. What's more, it only delays the inevitable for the first country which is never free from debt.