People in Iran have come out on streets to protest against increase of gasoline price. At least 36 people have died since protests erupted across the country.
"The United States supports the Iranian people in their peaceful protests against the regime that is supposed to lead them," the statement says.
Washington also condemns the use of lethal force and the stringent restrictions on communications used against demonstrators, the spokeswoman added.
Earlier in the day, Iranian Foreign Ministry slammed US Secretary of State, Mike Pompeo, for backing the protestors.
IRNA reported that "Foreign Ministry spokesman Abbas Mousavi on Sunday lambasted US Foreign Secretary Mike Pompeo's backing for a group of rioters in certain Iranian cities, saying that actions by a number of saboteurs have nothing to do with the nature of the Iranian intelligent and foresighted people."
Pompeo on Saturday in a tweet said that the US will be standing with people of Iran.
Mousavi criticised "such interfering actions" and stated that "Iran's noble nation knows well that such hypocrite statements are completely void of sincere sympathy".