"The Governing Council is comfortable with acting next time but before we want to see the staff projections that will come out in early June," Mario Draghi told a news conference after the ECB decided to keep its interest rates unchanged at 0.25 per cent.
He also flagged his concerns about the strength of the euro, which hit a 2-1/2 year high against the dollar as he was speaking.
Mr Draghi repeated the ECB's commitment to keeping monetary policy loose for an extended period of time.
"We will maintain high degree of monetary accommodation and act swiftly if required with further monetary policy easing," Mr Draghi said, adding that all options had been on the table at the meeting that decided to keep rates unchanged.
"We have received plenty of advice," he said."We are independent, so people should be aware that if this might be seen as a threat to our independence it could cause long-term damage to our credibility."
The euro, trading at 1.38 to the dollar, has gained more than 14 per cent over the US dollar since a July 2012 low.
Mr Draghi also said that the bank was on alert to the perils of euro strength. "Strengthening of the exchange rate in the context of low inflation is cause for serious concern in view of the governing council," he said.
"The governing council is unanimous in its commitment to using also unconventional instruments within its mandate."
ECB Governing Council met in Brussels against the backdrop of a Franco-German spat over ECB policy towards the euro's strength - one factor Mr Draghi has identified as a potential trigger for policy action.
France wants it act now to prevent continued low price inflation while industrially powerful Germany is apprehensive because its fears fresh bubbles - for example, in the cost of housing.
Financial markets have been embracing the euro as the economy has improved and with the debt crisis easing.
This is illustrated by the fact that despite a massive default on its debt roughly two years ago, Greece is already able to borrow again, albeit on a small scale.
Portugal, heavily in debt, has avoided a second international bailout to borrow normally on markets.
Investor enthusiasm for the euro is so great that even Africa's Nigerian neighbour Cameroon will issue a bond in the currency shortly.
But the rising demand has pushed the strength of the euro against currencies such as the dollar higher, another factor that could compound the problem of low prices because it makes it cheaper to import.
Germany's finance minister Wolfgang Schaeuble cautioned on Thursday against the dangers of easy central-bank money.
"We need to reduce excess liquidity to prevent new (speculative) bubbles from forming," he said.
Germany has said, however, that the level of the euro was an issue for the ECB but not politicians, indirectly criticising France's prime minister after he said the currency was "too high" and a "more appropriate" monetary policy was needed to bring it down.
Data have since shown euro zone inflation ticked up to 0.7 per cent in April from March's 0.5 per cent, relieving pressure on the ECB to act this month. But a downward revision in the staff inflation forecasts in June could trigger action next month.