Zimbabwe, locked out of international capital markets since defaulting in 1999, expects its stronger economy to help it pay back external creditors, without saying when this would begin.

Finance Minister Mthuli Ncube told reporters in the capital, Harare, on Tuesday that the country's debt as a percentage of gross domestic product has declined to 46% from around 60% thanks to better growth.

"You can be assured that given this larger GDP base this creates more opportunity and capacity for us to start servicing our external debt," he said, without providing a time-frame.

"The economy has grown to a point where it can allow us to begin servicing our debts sustainably."

Zimbabwe wants to restructure its $21 billion debt, of which around $12.3 billion is owed to external creditors including the World Bank, African Development Bank and the European Investment Bank.