FRANKFURT, Germany — Europe’s ailing economy will get a major dose of stimulus from the European Central Bank – a bond buying program designed to make loans and exports cheaper so companies can hire and expand.

Starting in March, the ECB will buy 60 billion euros’ worth of government and corporate bonds each month at least through September 2016. The 1.1 trillion euro program was an emphatic signal of the ECB’s willingness to do all it can to rejuvenate the economy shared by the 19-nation euro currency alliance.

ECB President Mario Draghi pledged Thursday to extend the bond buying if needed until the bank saw a significant upturn in the eurozone’s excessively low inflation, which threatens to become a downward spiral.

Stocks rallied in Europe and the United States after the ECB’s announcement, with the Dow Jones industrial average jumping 259 points, or 1.5 percent. The euro’s value, meanwhile, plunged nearly 2 percent against the dollar to its lowest level in 11 years in anticipation that the ECB’s bond purchases will drive down the currency. A lower-valued euro would make European exports more affordable overseas.

The ECB’s purchases will flood the economy with money that the central bank will create – a power it wields as the euro’s legal issuer. Its chief mandate is to maintain price stability. It’s fallen well short of its goal of 2 percent annual inflation, considered consistent with a healthy economy. The current rate is minus 0.2 percent.

Fears have spread that the eurozone could face chronic falling prices, or deflation. Though low or falling inflation is often welcomed by shoppers, it reflects sluggish demand and can paralyze an already weak economy – a problem that has long afflicted Japan, the world’s third-largest economy.

The eurozone is still working off a crisis over excessive government debt in countries such as Greece, Portugal and Ireland. The alliance’s economy has lagged even as the United States and Britain have recovered more robustly from the financial crisis and Great Recession. Unemployment is 11.5 percent across the currency union, and 26 percent in Greece. In the United States, by contrast, the unemployment rate is 5.6 percent.

Earlier Thursday, the ECB kept its main interest rate unchanged at a record low 0.05 percent.

There’s no guarantee that the ECB’s bond buying can succeed without further action by national governments in the currency union. Skeptics have suggested that the bond buying has been robbed of some of its potential effectiveness through delay and that Europe’s problems lie beyond the reach of monetary policy.

In Davos, Switzerland, German Chancellor Angela Merkel said before the announcement that “whatever decision the ECB makes, it must not distract from the fact that the actual impulses for growth from sensible conditions must be created, and can be created, by politicians.”

The ECB acted after months of excessively low inflation in the eurozone had discouraged borrowing and spending and kept the economy at risk of recession. The fate of the eurozone is vital for the global economy in part because Europe is a major trade partner for the United States, Britain, Eastern Europe, and Asia. And European officials have warned that stagnation must end if voters are to maintain their support for the shared currency.

The U.S. Federal Reserve launched three rounds of bond purchases that were credited with helping jump-start the U.S. recovery. The Bank of England and the Bank of Japan have also done bond purchases.

Draghi and the ECB governing council made a key concession to critics of massive government bond purchases: They said the risk of any losses would stay with national central banks for 80 percent of the bonds bought.

Draghi has faced opposition from two German members on the governing council. German Bundesbank head Jens Weidmann had argued that bond purchases could stick German taxpayers with losses in case of default.

And Weidmann complained that the new stimulus would take pressure off governments, such as those of France and Italy, to ease regulations on hiring and firing and make their economies more business- and growth-friendly.