FRANKFURT — The president of the European Central Bank on Thursday cited the rising value of the euro as a possible threat to the region’s economic recovery, comments that immediately sent the euro down sharply against the dollar and yen.

Mario Draghi, the E.C.B. president, denied that the central bank was trying to influence the value of the euro, no doubt mindful of provoking a currency war with Japan or the United States. But he then made statements that investors interpreted as meaning the E.C.B. could take action if the euro rose too much.

“The exchange rate is not a policy target, but it is important for growth and price stability,” Mr. Draghi said at a news conference after the regular monthly policy meeting of the E.C.B.’s Governing Council, in which the central bank left its main interest rate at 0.75 percent, as expected.

Separately, the Bank of England also kept its benchmark interest rate unchanged on Thursday, at 0.5 percent, amid worries that the British economy could fall back into a recession for the third time in five years. The pound has been falling against the euro and the dollar this year, pressured by investor concerns that the British economy may not manage to recover anytime soon.