ATHENS — Greek lawmakers voted on Wednesday to sharply reduce government spending and sell off an array of national assets, staving off default on the country’s debt and easing, for the moment, a crisis among countries that use the euro.

Markets rallied globally, and European leaders welcomed the passage of one of the most radical overhauls of the Greek economy since democracy was restored in 1974.

But the changes are deeply unpopular in Greece, where street protests continued, and the Socialist government of Prime Minister George A. Papandreou will need to overcome widespread skepticism that it can carry out the budget cuts, layoffs, tax increases and forced asset sales, beginning with a vote Thursday on putting the measures in effect.

Economists also expressed concern that the austerity program demanded by European and international lenders could end up pushing the Greek economy into a deeper slump, making its debt even harder to pay back. More broadly, critics said they doubted that Europe had done more than postpone a day of reckoning for the euro, with Ireland, Portugal and Spain, as well as Greece, all struggling with slow or negative growth and rising debts.