You can change and extend your visitor status from B-2 to B-1 by filing form I-539 with USCIS and paying the fee of $290. In addition, you should provide a written explanation as to why you need to change and extend your status. The maximum time that you can legally stay in the US as a visitor is 1 year. The application should be submitted 90 days or at least before your status expires.
Answered on Apr 02nd, 2013 at 3:15 PM