Below are the directions to apply for a U.S. visa to enter the United States.
All visa applicants must apply at a U.S. Consulate or Embassy and appear in person for an interview. It is not possible to apply for a visa in the United States. Visit the U.S. Department of State’s visa website for detailed information about visa types (e.g. J-1, H-1B, E-3 etc.), documentation requirements.
Find a U.S. Embassy or Consulate near you. Enter the name of the city where the consulate is located in the “Select a U.S Embassy or Consulate” search tool and find out how soon nonimmigrant visa interview appointments are available.
Important note: refer to the U.S. Embassy or Consulate’s website where you intend to apply for your visa stamp for definitive guidance on what documents you need to prepare to get your visa. Not all documentation requirements are the same at every consulate.
Depending on the agreements made between the US and your country of citizenship and the consular officer who interviews you, your visa will be granted for a specific length of time and a specific number of entries. You can search for your country of citizenship in the Visa Reciprocity Table online. In some cases, one visa will not cover the full length of the time you plan to be in the US. If your visa expires and you have plans to travel internationally, you will have to apply for a new visa stamp before re-entering the US.
Some US Consulates have backlogs for visa interview appointments. The Office of International Services (OIS) highly recommends scheduling your visa interview as soon as possible to avoid having to wait for an interview appointment. US Consulates usually have instructions for booking interview appointments on their web site.
If you intend to apply for a visa in a country other than your country of citizenship, be sure to check the US Consulate's web site to verify that they will issue visas for Third Country Nationals. Recent changes in visa issuance have led some countries to change their policies regarding issuing visas to Third Country Nationals.
Be aware, if you are in a research field that may be considered of US national security interest, you may face serious delays receiving a visa while a background check is being conducted. It is impossible to predict how long a background check might take (one week to 6 months), and it is not possible for any agency to intervene to expedite the background check. Read more about visa delays & security clearances here.