The bank said Thursday it was lowering the outlook for the eurozone economy this year to 1.9 percent from 2.0 percent in its previous forecast in September. The projection for 2019 was lowered to 1.7 percent from 1.8 percent.
The 19 countries that use the euro have seen growth ease to 0.2 percent in the third quarter from the previous quarter, down from stronger growth at the end of last year. Worries about trade conflict between the U.S. and China, a possible meltdown of government finances in Italy, and a potential disorderly exit by Britain from the EU have weighed on activity.
The European Central Bank is expected to halt the stimulus program that it deployed nearly four years ago to nurture a teetering eurozone economy back to health.
Analysts say the bank is likely to confirm Thursday its plan to stop the program's monthly bond purchases at year end despite worries about growth. The program pumped 2.6 trillion euros ($3 trillion) into the economy of the 19 countries that use the euro.
Attention will turn to President Mario Draghi's news conference for clues about whether the bank might postpone its first interest rate increase.
Draghi has credited the stimulus and low rates with creating 9.5 million jobs while Europe's economy healed from a debt crisis that threatened to break up the euro. But critics in Germany say it bailed out fiscally wobbly governments.