If you borrow, it's common sense to pay back!
However, if you are unable to pay back, you must explain the reasons for the plight you are in, and request for an extension of maturity dates.
South Korea recently requested North Korea to fulfill their long-overdue debt duties, but there is no response from North Korea.
(North Korea must pay back 720 million dollars by 2037, and 5.78 million dollars by 2013.)
Moreover, North Korea ignored the Korean government's request of payment, and enforcing provocations and threats against South Korea instead.
North Korea's actions are totally incomprehensible to a person or entity of commonsense.