President Bush has issued an executive order that renews sanctions barring U.S. firms from conducting business with Iran.
The announcement Monday extends by one year sanctions initially imposed by then-President Bill Clinton in 1995.
The executive order, which Mr. Bush has extended annually since 2003, prohibits most imports and exports between the U.S. and Iran, including dealings in Iranian crude oil.
A spokesman for the White House National Security Council, Frederick Jones, said the actions and policies of Tehran led to the continuation of sanctions. He said those include its support for terrorists, its "abysmal" human rights record and its pursuit of nuclear weapons.
The United States has maintained various sanctions against Iran since the seizure of the U.S. embassy in Tehran in 1979.
Some information for this report was provided by AFP and Reuters.