Federal Reserve Chairman Jerome Powell pushed back against the prospect the central bank would deploy negative interest rates in the U.S., though he didn’t fully rule out the option as a potential tool in the future.

“The evidence on negative rates is mixed,” Powell said Wednesday in answer to a moderator’s question after giving a speech via video. He noted Fed officials had debated whether to follow other central banks in that direction and opted to use other tools and said “for now it’s not something we’re considering.”

The S&P 500 fell at the open and traders pushed bets on a negative Fed benchmark rate later into next year as investors absorbed Powell’s speech, which highlighted the risks of lasting economic harm due to the coronavirus pandemic.

“I don’t think he could have been clearer, but market participants have not been willing to take ‘no’ for an answer yet, so I am not optimistic that the message will be absorbed this time either,” Stephen Stanley, chief economist at Amherst Pierpont Securities said in a note to clients.

--With assistance from Michael McKee.