The U.S. Mission/Embassy in Nigeria issues a travel advisory reminding Americans with dual nationality to enter and depart the United States using a valid U.S. passport. The advisory states that this requirement applies to all U.S. citizens, including children, who also hold citizenship of another country. It further warns that dual national U.S. citizens are not allowed to use a foreign passport to apply for the Electronic System for Travel Authorization (ESTA). According to the embassy, the U.S. Department of Homeland Security routinely denies or cancels ESTA applications submitted by dual U.S. citizens when they use foreign passports. The advisory also advises U.S. citizens living abroad to ensure they have valid U.S. passports before traveling, including renewing passports that are expired or close to expiration. In addition, it reminds travelers that some destination countries require passports to have at least six months of validity remaining before entry.