SINTRA, Portugal (AP) — Europe has made progress in strengthening its currency union, but needs more growth if the euro is to survive long term, a top U.S. Federal Reserve official said Thursday.

Fed Vice Chair Stanley Fischer said the euro's crisis has led to new institutions such as European Union-level banking supervision and procedures to wind up bad banks to spare taxpayers the costs of bailouts.

But Fischer warned that "in the longer run," the monetary union "will not survive unless it also brings prosperity to its members."

The eurozone has struggled with a crisis over too much government and bank debt since Greece reported its deficit was out of control in 2009. Greece, Portugal, Ireland, and Cyprus have been bailed out by other members, and Spain got a bailout for its banks.

European governments are facing low growth and high unemployment as they restrain spending to try to reduce heavy levels of debt. Governments in France and Italy are struggling to make their economies more business-friendly.

Fischer's talk explored the oft-repeated thought of French economic and political figure Jean Monnet that European integration would be "forged in crises." Fischer said that recent measures taken to strengthen the 16-year-old euro — such as EU level supervision carried out by the ECB — would probably not have been agreed on by political leaders without the euro crisis.

But he said that the union faced further challenges, such as the lack of a common budget. Leaving budget decisions to individual governments risks overspending by some. It also deprives the union of a common pot to even out recessions in individual countries, as the U.S. federal budget does for U.S. states.

"The decision to use the single currency to drive the European project forward was a risky one, and at some stage or probably in several stages, it will be necessary to put the missing fiscal framework into place," Fischer said.

European political leaders however can't agree on a common fiscal pot.

Fischer spoke Thursday at a conference on unemployment and inflation convened by the European Central Bank in Sintra, Portugal.

His basic sentiment about growth won endorsement from ECB head Mario Draghi, who said that "growth is too low everywhere."