Visitors traveling to the United States are required to be in possession of passports that are valid for six months beyond the period of their intended stay in the United States. Citizens of the countries listed below are exempt the six-month rule and need only have a passport valid for their intended period of stay.

In any case, your passport must be valid on your entry into the U.S. If your passport expires during your stay in the U.S., you need to get it renewed or get new one from the embassy or consulate of your country in the U.S. If you are on a short visit to the U.S. (such as on tourist visa, business visa etc.), it would be best to get your passport renewed before arrival into the U.S., otherwiswe, you will be admitted into the U.S. until the expiration date of the passport.

Algeria
Andorra
Antigua and Barbuda
Argentina
Australia
Austria
Bahamas, The
Bangladesh
Barbados
Belgium
Bermuda
Bolivia
Bosnia-Herzegovina
Botswana
Brazil
Bulgaria
Canada
Chile
Colombia
Costa Rica
Cote d'Ivoire
Croatia
Cuba
Cyprus
Czech Republic
Denmark
Dominica
Dominican Republic
Ecuador
Egypt
El Salvador
Eritrea
Estonia
Ethiopia
Fiji
Finland
France
Georgia
Germany
Greece
Grenada
Guatemala
Guinea
Guyana
Hong Kong (Certificates of Identity and Passports)
Hungary
Iceland
India
Ireland
Israel
Italy
Jamaica
Japan
Korea
Kuwait
Laos
Latvia
Lebanon
Liechtenstein
Luxembourg
Macau
Macedonia
Madagascar
Malaysia
Malta
Mauritius
Mexico
Monaco
Netherlands
New Zealand
Nicaragua (for all passports)
Nigeria
Norway
Oman
Pakistan
Panama
Paraguay
Peru
Philippines
Poland
Portugal
Qatar
Romania
Russia
San Marino
Senegal
Serbia and Montenegro
Singapore
Slovak Republic
Slovenia
South Africa
Spain
Sri Lanka
St. Kitts and Nevis
St. Lucia
St. Vincent and The Grenadines
Suriname
Sweden
Switzerland
Syria
Taiwan
Tanzania
Thailand
Togo
Trinidad and Tobago
Tunisia
Turkey
Tuvalu
United Arab Emirates
United Kingdom
Uruguay
Uzbekistan
Vatican (Holy See)
Venezuela
Zimbabwe