The European Central Bank said Thursday that it would close its controversial bond buying program at the end of this year but plans to reinvest maturing securities for "an extended period of time" as it attempts to keep markets rates low amid signs of slowing economic growth.

The Bank said its Asset Purchase Program, which has scooped up more than €2.6 trillion in government, agency and corporate bonds over its near four-year lifespan, would end on December 31. The bank also made no changes to its key interest rates, including the -40 basis point charge it applies to cash left in its overnight deposit facility, and said rates would remain "at their present levels at least through the summer of 2019."

"The Governing Council intends to continue reinvesting, in full, the principal payments from maturing securities purchased under the APP for an extended period of time past the date when it starts raising the key ECB interest rates," the ECB said in a statement. "And in any case for as long as necessary to maintain favourable liquidity conditions and an ample degree of monetary accommodation."

The euro was marked modestly lower against the U.S. dollar at 1.1345 following the ECB statement, with investors now focused on President Mario Darghi's press conference at 8:30 eastern time, in which he is expected to trim growth and inflation forecasts for 2019 as he heads into the final year of his eight year tenure in Frankfurt.