Dubbed the "Santa Claus rally," stocks often surge in the week between Christmas and New Year.
But Joe Tatusko, chief investment officer for Westport Resources, a financial planning firm in Connecticut, said that futures were slipping on Friday because many individuals are selling stocks to reduce their tax bills.
"It's a darn good time to do some tax loss selling," he said.
Earlier this month the Fed announced that it will modestly reduce its bond buying program in January. But many experts believe the bull market will continue for a sixth year in 2014, albeit at a more modest pace.
European markets rose in morning trading, led by a 0.7% rise on Germany's DAX. London's FTSE gained 0.5% and France's CAC 40 put on 0.6%.
Asian markets ended the week on a positive note. China's Shanghai Composite rose 1.4% and Hong Kong's Hang Seng Index added 0.3%.