ECB policymaker Kocher said she stands ready to take monetary policy action at any time if needed.

Three days after its U.S. listing, SK Hynix ADRs are trading at about a 46% premium to Korea-listed common shares, approaching 50%. The ADR surged as much as 23% on Tuesday after a record sell-off in Korea the prior day had pushed the ADR down more than 9% in U.S. trading. The premium has widened sharply from the roughly 3% spread set at issuance. An SEC filing shows one ADR represents one-tenth of a common share. The rebound coincided with the start of U.S. options trading on the ADR, increasing access for derivatives traders.

Federal Reserve Chair Kevin Warsh said a broader price-stability goal remains on his mind; he will assess whether further reforms are needed and hopes price moves will quiet public discussion.