In a travel alert issued today, the department said it was not aware of specific threats to US interests related to the Games that begin next month.
But it said large events like the Olympics are "an attractive target for terrorists" and Americans should be aware of their surroundings and "exercise good judgment and discretion" if they use public transportation.
It noted that Russia has vowed to take appropriate security steps. But it also pointed out several recent terrorist attacks on public transport in the city of Volgograd while also making clear those occurred 600 miles (965 kilometers) from Sochi.