Definition: Collateralization of external debt
External debt - IMF
To provide additional assurance to the creditor, the debtor may set aside either financial assets or future streams of income as collateral for the debt incurred. I n other words, payments on the debt might be "backed" by future export earnings, such as receipts from petroleum sales, or the creditor may have a claim on certain financial assets held with third parties if the debtor defaults. Alternatively, the debtor might invest funds in a zero-coupon instrument that at maturity will equal the value of the principal debt incurred, which is then due for repayment. In all cases, external debt should be recorded gross—that is, separately from the collateral. For instance, where the debtor has invested funds in a zero-coupon bond, both the external debt and the zero-coupon bond are recorded on a gross basis, the zero-coupon bond being an asset of the debtor. Also, when debt is contractually to be serviced by an income source of the debtor (for example, future export earnings), the debtor continues to record the receipt of income and the payment of principal and/or interest even if the income is passed directly from "source" (for example, the purchaser of the exports) to the account of the creditor, without directly involving the debtor. There may well be analytical interest in information on the value of external debt that has been collateralized, and in the type of financial asset or income stream used to back the external debt.
International Monetary Fund (IMF), "External Debt Statistics: Guide for Compilers and Users; Appendix I. Specific Financial Instruments and Transactions: Classifications", Washington D.C., 2003