FRANKFURT, Germany — A member of the European Central Bank’s rate-setting committee says that it is time to start phasing out the bank’s bond-purchase stimulus efforts.

Klaas Knot, the head of the Netherlands’ central bank and a member of the ECB’s 25-member governing council, says in a speech released Wednesday that 12 quarters of growth in the 19 countries that use the euro means that “the main rationale for central bank asset purchases has disappeared.”

ECB President Mario Draghi said Sept. 7 that the bank could offer plans at its Oct. 26 meeting for eventually ending its 60 billion euros in monthly purchases. Draghi has been cautious about stimulus withdrawal for fear of roiling markets.

Knot said that while ending the program posed “challenges” he saw “no reason to be overly dramatic.”