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How to Renew a Tourist Visa Without Leaving the U.S.
B-2 “Tourist” visas are generally issued for a period of six months. With approval from the U.S. Citizenship and Immigration Services (USCIS) the tourist visa may be extended a maximum of 6 months.
When to Apply for the Tourist Visa Extension
It is recommended that you apply to extend your stay at least 45 days before your original authorized stay expires, but the USCIS Service Center must receive your application no later than the day your authorized stay expires.