Here's the full statement from White House NSC spokesperson Caitlin Hayden (emphasis added):
The United States condemns the terrorist attacks that struck the Russian city of Volgograd and sends deepest condolences to the families of the victims with hopes for the rapid healing of those wounded.
The United States stands in solidarity with the Russian people against terrorism. The U.S. government has offered our full support to the Russian government in security preparations for the Sochi Olympic Games, and we would welcome the opportunity for closer cooperation for the safety of the athletes, spectators, and other participants.
The Winter Olympics are about 40 days away, and Russia is reeling from the latest two attacks. Never has a host country been the scene of so much violence so close to the Games.