For trade treaty visas you need to be a citizen of a country with a trade treaty with the United States. Or check the Foreign Affairs Manual. Check website: foia.state.gov/regs/search.asp.
Countries with a treaty are as follows:
-A-
Albania
Argentina
Armenia
Australia
Austria
Azerbaijan
-B-
Bahrain
Bangladesh
Belgium
Bolivia
Bosnia and Herzegivina
Bulgaria
-C-
Cameroon
Canada
Chile
Colombia
Congo
Costa Rica
Croatia
Czech Republic
-E-
Ecuador
Egypt
Estonia
Ethiopia
-F-
Finland
France
-G-
Georgia
Germany
Grenada
-H-
Honduras
-I-
Ireland
Italy
-J-
Jamaica
Japan
Jordon
-K-
Kazkhstan
Korea
Kyrgystan
-L-
Latvia
Liberia
Lithunia
Luxembourg
-M-
Macedonia
Mexico
Moldova
Mongolia
Morocco
-N-
Netherlands
Norway
-O-
Oman
-P-
Pakistan
Panama
Paraguay
Philippines
Poland
-R-
Romania
-S-
Senegal
Singapore
Slovenia
Spain
Sri Lanka
Suriname
Sweden
Switzerland
-T-
Thailand
Togo
Trinidad and Tobago
Tunisia
Turkey
-U-
Ukraine
United Kingdom
-Y-
Yugoslavia