Investors have soured on the latest attempt to resolve the European debt crisis.

Stocks tumbled around the world, the euro slid to an 11-month low and borrowing costs spiked for heavily indebted Italy. The markets’ jitters reflect rising doubts about the deal European Union leaders reached at a summit last Friday in Brussels.

The agreement requires the 17 countries that use the euro and nine other EU countries to balance their budgets and gives the International Monetary Fund up to 200 euros ($264 billion) to help countries with high debt loads.

But there’s growing disappointment that the new EU treaty:

• Doesn’t reduce existing government debt levels;

• Doesn’t do much to promote the long-term growth that would shrink those burdens;

• Doesn’t provide enough money to reassure financial markets that Italy and Spain won’t default on their debts.

It was also unclear how the treaty would be enforced and whether some of the countries that signed on might end up dropping out because of resistance to budget cuts back home. Britain has refused to sign the treaty.

“Markets like quick fixes and have no patience with the length of the political processes,” said Gianni Toniolo, a professor of economics and history at Duke University.

The euro traded below $1.30 for the first time since January 12, hitting a low of $1.2973. Some of that is loss of confidence in the assets of the 17 euro nations, but it’s also the result of two quarter-point interest rate cuts from the European Central Bank. The cuts lower the return on euro-denominated holdings and can induce investors to move money elsewhere.

European stock markets fell broadly. Germany’s DAX dropped 1.7 percent; France’s main stock index lost 3.3 percent.

Italy held its last bond auction of the year on Wednesday and it didn’t go well. Investors demanded even more money to lend to the eurozone’s third-largest economy. Italy paid 6.47 percent interest to borrow 3 billion euros ($3.95 billion) for five years, up from 6.30 percent just a month ago.

The higher rates reflected investors’ fears over the inadequacy of last week’s agreement to keep eurozone governments from piling up more debt in the future. Italy has a staggering 1.9 trillion euros ($2.5 trillion) in outstanding debt, and its economy is too large for Europe to bail out. Greece, Ireland and Portugal have been bailed out.