Access to capital markets can be cut off because a country’s credit rating falls or because the market itself is short of liquidity. In addition, access may be so costly as to be prohibitive. In these circumstances, central banks can be pressed into drawing on international reserves.
Though building  6  BIS Review 1/2006  foreign exchange reserves by way of foreign borrowing is not the optimum approach to foreign exchange accumulation, in some circumstances countries may need to resort to the capital markets in order to boost reserves, in order to fund foreign currency payments and to boost confidence in the economy.