FRANKFURT, Germany (AP) — European Central Bank head Mario Draghi says the eurozone economy still faces "risks and uncertainties" — including a looming trade dispute with the United States — despite stronger growth, and has cautioned that inflation needs to rise further before monetary stimulus is ended.

Draghi said Wednesday that higher inflation, not growth, is the "very clear condition" for the central bank to end its bond-buying stimulus program, and that risks to the outlook remain. Inflation of 1.2 percent annually is short of the bank's goal of just under 2 percent considered best for the economy.

Inflation could stay low if slack remains for longer in the economy and the labor market. And a protracted trade conflict could hurt growth.

Draghi said that tariffs' "first round effects are likely to be small." U.S. President Donald Trump has announced new import taxes of 25 percent on steel and 10 percent on aluminum. But Draghi warned that after that the "second round effects could have much more serious consequences" if the European Union retaliates and the dispute spreads trade restrictions to other categories of goods. That in turn could hit business confidence and investment.

The European Central Bank, the top monetary authority for the 19 countries that use the euro as currency, has said its 30 billion euros ($37 billion) in monthly purchases will continue at least through September, but has given no fixed end date. Annual growth has strengthened to 2.7 percent in the fourth quarter.

Speaking at a conference at Frankfurt's Goethe University, Draghi echoed earlier cautious comments by saying that monetary policy needs to be "patient, persistent and prudent." He said that the central bank would stick to its guidance on the sequencing of the next steps, meaning that the first interest rate increases will start well after the end of the bond purchases. That would put them off until at least 2019. Currently the bank's benchmark short-term rate is at a record low zero.