Also spurring the gains was a separate move by China's central bank to support economic growth.
The European Central Bank, U.S. Federal Reserve, the Bank of England and the central banks of Canada, Japan and Switzerland are taking joint action to make it cheaper for banks to get U.S. dollars if they need them.
Futures for the major indexes rose more than 2 percent. Less than two hours before U.S. markets open, Dow futures are up 256 to 11,821. Futures for the broader S&P 500 are up 30 points to 1,227.