First Determine What Type of Visa You Entered the U.S. On
This will depend on a variety of factors. In most cases it will be advisable for the visitor to return home to wait for the visa petition approval, then apply for the visa stamp at a local U.S. Consulate. If the individual entered on the "Visa Waiver Program" (indicated by a green-colored I-94 entry card), he or she MUST leave the U.S. and reenter in the new nonimmigrant work visa category. When foreign nationals visit the U.S. as tourists or on business trips, they have stated to the U.S. government that their intentions are to stay temporarily. Therefore, it is not advisable to request to change status shortly after arrival as it suggests that the statements made at the time of entry were not truthful.
Visa Waiver Entries
Nationals of certain countries do not need to obtain visas for business visits to the U.S. for 90 days or less for purposes acceptable in the B-1 category. They may enter without a visa pursuant to the Visa Waiver Program. An individual who enters the U.S. through this program is NOT eligible for an extension of stay or change to a different status and MUST leave the U.S. within 90 days of entering.
The ability to visit the U.S. without a visa is currently available to citizens of the following countries: Andorra, Australia, Austria, Belgium, Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Korea, Liechtenstein, Luxembourg, Monaco, The Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden, Switzerland, United Kingdom.