(CNN) -- European Union leaders on Saturday called for a "stabilization mechanism" in hopes of easing markets shaken by the Greek economic crisis before they re-open Monday.

"Taking into account the exceptional circumstances, the (EU) commission will propose a European stabilization mechanism to preserve financial stability in Europe," said EU President Herman Van Rompuy.

The proposal will be submitted for approval at an emergency meeting of the EU's Economic and Financial Affairs Council on Sunday, he said.

The group will also combat "without mercy, speculation by regulating financial markets," French President Nicolas Sarkozy said. "We are absolutely determined to fight speculation by reinforcing financial regulation."

"Today was the moment of truth ... either we would let the markets, instead of us, decide the fate of the Euro, or we would be capable of taking the appropriate measures to combat speculation and to exit this crisis stronger and more unified. That's what we decided tonight."

The meeting in Brussels came in the wake of Greek lawmakers approving a package of budget-cutting measures to help the country's battered economy -- measures that were required to meet the terms of a €110 billion ($140 billion) bailout. Rompuy said the Greek government has signaled it is committed to "the full implementation of these vital reforms."

Under the agreement, the European Union will give 80 billion euros as part of a joint package with the International Monetary Fund. Greece will receive the first installment sometime before May 19.

"The program adopted by the Greek government is ambitious and realistic," Rompuy said. "It addresses the grave fiscal imbalances, will make the economy more competitive, and will create the basis for stronger and more sustainable growth and job creation."

In Washington, U.S. President Barack Obama on Friday said he spoke with German Chancellor Angela Merkel regarding economic and financial developments in Europe.

"We agreed on the importance of a strong policy response by the affected countries and a strong financial response from the international community," he said. "I made clear that the United States supports these efforts and will continue to cooperate with European authorities and the [International Monetary Fund] during this critical period."

European Central Bank officials have tried to play down fears that the economic turmoil in Greece could spread to other heavily indebted European countries like Spain, Portugal and Italy.

Spain saw three straight days of losses in its stock market this week after the country's credit rating was downgraded by the influential rating agency Standard & Poor's.

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The Spanish government fired back on Friday, threatening to bring "legal action" against speculators accused of launching "attacks" against the economy.

Luis de Guindos, an economist at the IE Business School in Madrid and a former secretary of state for the economy, said, "This is the deepest and most profound crisis we have had in Spain in five decades, since the Spanish Civil War."

In a possible glimmer of hope, the Bank of Spain announced Friday that the nation's economy grew 0.1 percent in the first quarter of 2010.

"It's slightly positive, one decimal point," de Guindos said. "We need some positive news to improve the mood of Spanish society."