Updated at 4:05 p.m. ET: Stocks closed Wednesday mixed as minutes from the latest meeting of the Federal Reserve indicated the central bank was ready to pull the trigger on another round of stimulus.
Minutes from the July 31-August 1 meeting showed the Fed is likely to deliver another round of monetary stimulus "fairly soon" unless the economy improves considerably.
"This is quite a surprise, this announcement, and you are seeing the market react a bit favorably towards it," said Tim Ghriskey, chief investment officer of Solaris Group in Bedford Hills, New York.
"It means they are simply waiting, they feel like they have the firepower. Clearly, at least many Fed officials have stated they do believe it will benefit the economy and they are ready to use that firepower if necessary."
Stocks were lower for most of the session after weak export data from Japan and Greece's meetings this week with European Union officials gave investors reasons to pull back after the recent rally.
Japan's exports slumped the most in six months in July as shipments to Europe and China tumbled, adding to global demand concerns while.
Uncertainty lingered over the effectiveness of Greek Prime Minister Antonis Samaras' attempts to convince other European officials his country should be given more time to meet targets for deficit cuts.
The S&P 500 hit its highest level in more than four years on Tuesday but failed to hold peak and the index closed in the red.
However, its steady move higher has lifted short-term support to the 1,400 level, although the index may need a positive catalyst to extend the rally.
The Jackson Hole, Wyoming, meeting of central bankers and economists at the end of the month is seen as possibly the next big market catalyst, followed by the European Central Bank's September 6 meeting and the German constitutional court's vote to ratify the euro zone rescue fund six days later.
Among the most traded U.S. stocks Wednesday was Dell, lower day after the No. 2 U.S. PC maker warned of a challenging second half and slashed its full-year earnings outlook.
Toll Brothers shares rose to their highest since February 2007 after the largest U.S. luxury homebuilder reported a higher quarterly profit and a sharp jump in new orders.
Continuing a string of bullish housing sector data, U.S. home resales rose in July as low interest rates and a modest improvement in the labor market helped home buying conditions.
Reuters contributed to this report.