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Spain gave no hints Friday on when it might make a formal bailout request to trigger a new European Central Bank bond buying program that could ease the pressures on its economy.

But investors gambling it will come soon sent the nation's borrowing costs down to levels not seen in four months.

Deputy Prime Minister Soraya Saenz de Santamaria dodged repeated questions from reporters asking whether Spain would ask for the help, saying over and over again that officials will study the new bond-buying plan from the ECB, outlined Thursday by its president Mario Draghi, before making a decision.

"These matters must be analyzed calmly and carefully," she said at a weekly government news conference. "They have important implications for our country and our future."

The centerpiece of the plan — the ECB's most ambitious response yet to Europe's debt crisis — is a commitment to buy unlimited amounts of short-term bonds from euro countries that request help. The plan is meant to ease the financial pressures on Spain and Italy, the third- and fourth-largest economies in the eurozone, by giving them time to reduce their debt and reform their economies.

The ECB bond buying program will be discussed at next week's meeting of European finance and economy ministers in Cyprus, Saenz de Santamaria said.

Investors think Spain will make a formal request to tap the new program within weeks.

Those expectations have seen Spain's cost of borrowing fall sharply from the sort of levels that forced Greece, Portugal and Ireland to seek public finance bailouts. The yield on Spain's benchmark 10-year bond fell 0.32 percentage points on Friday to 5.68 percent, the first time that it's gone below 6 percent since May. A rate above 7 percent is widely-considered unsustainable in the long-run.

Spain's government has been pressing for months for the ECB to buy Spanish bonds, but has stressed that it shouldn't be forced to impose more austerity measures it says could choke growth and fuel social unrest.

But the ECB said countries that want to participate in the program must request it from the eurozone's bailout funds first, and will face strict conditions plus oversight from the International Money fund to make sure they don't backslide on promises to cut their debt levels.

Spain is stuck in a deep recession with unemployment of nearly 25 percent.

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Harold Heckle contributed from Madrid.