The interest rates for Spain and Italy's benchmark 10-year bonds are rising sharply, signaling resurging investor concern that Europe's sovereign debt crisis is far from over.

The rate, or yield, for the Spanish bond was up 0.16 percent to a dangerous 6.9 percent at midday Friday. Such borrowing rates are deemed unsustainable over the long term and could push Spain to seek a full-blown bailout like Greece, Ireland and Portugal.

Italy's rate was up 13 basis points to 6.01 percent.

Both countries' yields fell sharply last week in a wave of euphoria following a European Union agreement to channel aid directly to troubled banks without further burdening a country's debt and making it easier for EU fund systems to buy secondary market bonds so as to ease yields.