The European Central Bank will not stop short in rolling out its €1 trillion money printing scheme, its president said, playing down fears that quantitative easing could blow price bubbles. 

Mario Draghi's clear commitment was delivered in a speech at the International Monetary Fund in Washington. 

His comments show there is little prospect of paring back the fledgling programme that was launched despite the reservations of euro zone paymaster Germany. 

"After almost seven years of a debilitating sequence of crises, firms and households are very hesitant to take on economic risk," Draghi told an audience that included IMF chief Christine Lagarde. 

"For this reason quite some time is needed before we can declare success," he said.

Draghi did not comment on tense debt talks underway between Greece and international creditors, which remain a key threat to the euro zone economy. 

Draghi said that although the ECB's €60 billion a month of purchases, chiefly of government bonds, were lifting asset prices and confidence, he also wanted them to boost investment and price inflation. 

"We will implement in full our purchase programme as announced and, in any case, until we see a sustained adjustment in the path of inflation," he said. 

The Italian head of the ECB also responded to critics who argue that such money printing, or quantitative easing (QE), could fuel price bubbles in property or sap savings, playing down such concerns. 

"At the moment there is little indication that generalised financial imbalances are emerging," he stated. 

But Draghi said that policymakers must be very careful when the time comes to close the tap on easy money policies. 

This is because extended periods of money printing can lead investors to sink cash into assets that in more normal times can be more difficult to easily sell. 

"Exiting from abundant liquidity policies has to be done very, very carefully," Draghi said following a speech in Washington. 

He said when these policies stay in place for a long time, they become "rooted more and more" in investors' minds. 

The ECB chief recently described speculation that the QE scheme, which is due to last until September 2016, would be scaled back as surprising.