The European Central Bank says it is ready to buy the government bonds of the continent's debt-ridden countries, a move that could ease the rising borrowing costs of financially troubled Spain and Italy.

Bank President Mario Draghi did not disclose the size of the bond purchases, but said Thursday it would be sizeable enough for the bank to “reach its objective” of stabilizing borrowing costs in the 17-nation euro currency union. He said details of the bond purchases would be worked out “in the coming weeks.”

Both the Madrid and Rome governments have struggled to contain their borrowing costs — with the interest rates on Spain's debt topping the level at which Greece, Ireland and Portugal all were forced to secure international bailouts.

Some analysts have said the economic problems in the eurozone imperil the existence of the currency. But after bank policy makers met in Frankfurt, Draghi declared, “The euro is irreversible.”

The central bank, as expected, decided to keep its key benchmark interest rate at a record low of three-quarters of a percent. But to date the low rate has had little effect in spurring growth in the eurozone, with several countries mired in recessions and coping with high unemployment.

The eurozone debt crisis is now in its third year. A variety of measures adopted by the continent's political leaders have failed to quell the financial uncertainty. As a result, some financial traders, like Greece's George Tselios, have looked to the central bank for decisive action.

“The ECB must stop being just a regulator of currency circulation and a guarantor of inflation in the eurozone, it must do something more and become a guarantor of a smooth and good path for the euro.”