Mario Draghi said the European Central Bank (ECB) won't hesitate to add fresh stimulus, if needed, once it has a clearer picture of the economic impact from the U.K.'s vote to leave the European Union.

"If warranted to achieve its objective, the Governing Council will act by using all instruments available within its mandate," the ECB president told reporters in Frankfurt on Thursday. "I would stress readiness, willingness, ability, to do so."

The risk for the euro area is that its recovery might prove too fragile to cope with any downturn in trade and investment as a consequence of the Brexit vote. Even so, after calming market volatility with pledges of liquidity, officials have bought themselves time to judge how much further they can push their unprecedented easing, especially in the absence of more support from government policies.