The European Central Bank on Thursday launched its most aggressive effort to date to revive the region's ailing economy — a program to buy 1.1 trillion euros in government and private bonds starting in March.

The long-awaited program was an emphatic statement of the central bank's willingness to do all it can to rejuvenate the economy shared by the 19-nation euro currency alliance. And it showed the multinational ECB's readiness to assert its independence against critics in Germany, the eurozone's largest and most politically influential country.

The ECB said it would combine purchases of government bonds with an existing smaller program of private bond purchases, to total 60 billion euros a month through September 2016. All told, the program will amount to 1.1 trillion euros ($1.16 trillion).

By pumping new money into the eurozone's banking system, the ECB's bond purchases should make loans cheaper and easier to get so companies can invest, expand and hire.

The size of the program exceeded investor expectations, and ECB President Mario Draghi pledged to keep it going until the central bank sees a "sustained adjustment" in the path of inflation — in other words, for as long as it takes. The U.S. Federal Reserve made a similar vow with its bond-purchase programs, which were credited with helping lower unemployment and jump-starting the US recovery.

The value of the euro immediately fell on anticipation that the new money the ECB will pump out will drive down the currency's value. A lower-valued euro would make European exports more affordable overseas and could lift inflation above dangerously low levels.

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

Fears have been spreading that the eurozone could face a period of chronic falling prices, or deflation, that can paralyze an economy. There's no guarantee that the bond buying can succeed without more action by national governments in the currency union. Skeptics have suggested that the program has been robbed of some of its potential effectiveness through delay and that Europe's deeper problems lie beyond the reach of monetary policy.

"We shouldn't get carried away with the scale," said Luke Bartholomew, investment manager at Aberdeen Asset Management. "It may boost inflation expectations at the margin, but will probably only have a small positive effect on Europe's real economy. "

"A weaker euro should help exports a little, but it won't suddenly make European economies much more competitive. That urgently requires structural reforms which European leaders seem unwilling to push through. "

In Davos, Switzerland, German Chancellor Angela Merkel said shortly ahead of the ECB's decision 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."

"We have a lot of progress in many countries, particularly those that have been through a (bailout) program — we have reform efforts in Italy, I say finally ... those are important signals," Merkel said. "We have a new course, directed toward business, in France — that is good news. But we have also wasted a lot of time, and time is pressing."

The ECB finally acted after months of excessively low inflation in the eurozone that has 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. The ECB acted after the U.S. Federal Reserve completed three bond buying programs late last year. 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 he complained that the new stimulus would take pressure off governments such as those of France and Italy to impose reforms to cut regulation on hiring and firing and make their economies more business- and growth-friendly.

Draghi said it would be "a big mistake" for euro countries to view the ECB's bond-buying program as an a rationale to increase government spending.

"That would undermine confidence," he said.

Economists note that government bond yields have already fallen substantially since the depths of the eurozone's debt crisis in 2012. That means it will be hard to drive bond-market borrowing costs down much more. Meanwhile, banks — the main source of credit for eurozone companies — will get more cash, but any economic pickup depends on whether businesses see a reason to borrow and expand.

The eurozone is still working off a crisis over too much government debt. Growth has been sluggish as governments in countries such as Italy, Spain, Greece, Portugal and Ireland, which have had to restrain spending and raise taxes to try to reduce debt. European leaders have warned that the eurozone must end its stagnation to win lasting public approval for the shared currency.