"We call on (North Korea) to refrain from provocations, abide by their obligations under U.N. Security Council Resolutions, and remain engaged in substantive and sustained negotiations to do their part to ensure peace and stability on the Korean Peninsula and achieve denuclearization," a state department spokeswoman said in Rome.
U.S. Secretary of State Mike Pompeo is visiting Italy.
South Korea has said Wednesday's missile may have been launched from a submarine. The move came the day after North Korea announced a resumption of talks with the United States aimed at ending its nuclear program.