While recognizing the existence of dual nationality, the U.S. government does not encourage it as a matter of policy because of the problems it may cause. Dual nationality may hamper efforts by the U.S. government to provide consular protection to individuals overseas, especially when they are in the country of their second nationality. Claims of other countries upon dual national U.S. citizens may place them in situations in which their obligations to one country conflict with the laws of the other.
Public inquiries about the citizenship laws of other countries should be directed to the embassy or consulate of that country in the United States. U.S. law and regulations require that U.S. citizens enter and exit the United States on a U.S. passport, with certain limited exceptions.
Please visit travel.state.gov for more information on dual nationality.