"Our concern with Iran's development of space launch vehicle technologies are obviously well-known," State Department spokeswoman Victoria Nuland said, adding she could not confirm whether the launch had really taken place.
"Any space launch vehicle capable of placing an object in orbit is directly relevant to the development of long-range ballistic missiles as well as SLV (small launch vehicle) technologies, and they're all virtually identical and interchangeable."
Iranian Defense Minister Ahmad Vahidi told state television on Monday that his country had taken "a big step" towards sending astronauts into space by 2020 by launching a monkey into a sub-orbital flight and returning it safely.
Arabic-language channel Al-Alam and other Iranian news agencies said the monkey returned alive after traveling in a capsule to an altitude of 120 kilometers (75 miles) for a sub-orbital flight.
"This success is the first step towards man conquering the space and it paves the way for other moves," General Vahidi said, but added the process of putting a human into space would be a lengthy one.
But Nuland stressed that UN resolution 1929 "prohibits Iran from undertaking any activity related to ballistic missiles capable of delivering nuclear weapons, including launches using ballistic missile technology."
The United States would "continue to work closely with our partners and our allies to address our concerns about Iran's missile developments," she added.