Travel to Belgium from U.S
Belgium is part of the Visa Waiver Program, which enables citizens of Belgium to travel to the United States without a visa. On January 12, 2009, ESTA (the Electronic System for Travel Authorization) became a requirement of the Visa Waiver Program. ESTA is an application system for all travelers from Visa Waiver Countries, including Belgium. The Visa Waiver Program has simplified travel to the United States for millions of visitors by only requiring a machine readable passport. Now, due to heightened security regulations, the same visitors must apply for a Travel Authorization (ESTA) in advance. As always, a machine-readable or e-passport from a Visa Waiver country is still required to gain admittance into the country. The entire ESTA application process is conducted online and operated by the U.S. Department of Homeland Security (DHS).
The Travel Authorization is not a visa. In fact, a person from a non-visa waiver country should not even attempt to apply for a Travel Authorization. The purpose of ESTA is to allow DHS to pre-screen all Visa Waiver Travelers before they leave their respective countries. U.S. bound Belgium travelers are recommended to apply for the Travel Authorization at least 72 hours prior to departure. An approved Travel Authorization does not guarantee entry, but is a prerequisite to travel to the United States by air or sea carrier.
Source: www.esta.us