Upvote:1
You can only enter with the status you have a visa for. In other words, if you have an F-1 visa that allows you to go to the US border and seek admission under F-1 status. F-1 status is only for people studying full-time at a SEVIS-accreddited school in America. To be admitted under F-1 status, you need a valid I-20 from the international students office. You cannot enter under F-1 status just to go to a conference.
If you are studying outside the US, and simply need to visit the US for the conference, you need to enter under B-1 visitor status. That means you need a B-1 or combination B-1/2 visa, unless you are a national of Canada or a Visa Waiver Program member country.