“I tried to register under ESTA and my travel was not authorized. What do I do now?”
If your registration under ESTA is not authorized, you will require a visa in order to travel to the United States. Information about applying for a visa is available from the Embassy website: http://london.usembassy.gov/niv/apply.html.
Remember, you don’t need to have firm travel plans in order to apply for a visa, in fact, we recommend that applicants do not make irreversible travel plans until their application has been fully processed and they have the visa in hand.
You can also check out this video by the U.S Ambassador to the UK, Matthew Barzun, for more information.