Referring to a policy known as quantitative easing or QE, Draghi said at a news conference that "the asset purchase programme provides sufficient flexibility in terms of adjusting the size, composition and duration of the programme".
It was "intended to run until the end of September 2016, or beyond, if necessary," he added.
Fears of deflation -- a dangerous spiral of falling prices -- persuaded the ECB to launch in March the QE programme, under which it plans to purchase 60 billion euros (USD 68 billion) of sovereign bonds each month until September 2016, or 1.14 trillion euros in all.
But euro-area inflation still stood at only 0.2 percent in August, way off the two percent level which the ECB regards as conducive to healthy economic growth. And that target may not be attainable until 2018.
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Asked about the modalities of extending the programme, Draghi said it was still too early to say.
"We're not there yet," and the modalities had not been discussed by the governing council at Thursday's meeting, the ECB chief said.
The ECB would assess whether the economic slowdown in China and the decline in oil prices -- both putting a drag on the eurozone economy -- were only transitory or were here to stay, Draghi said.