According to the Decree No. 1008/2005 and the amendments to it introduced by the Decree No. 1175/2005 the US citizens do not need a visa to enter Ukraine if the period of their stay does not exceed 90 days.
Requirements For Foreign Citizens To Enter Ukraine
For the US citizens who enter Ukraine with the purpose of employment, permanent residency, study and work at the diplomatic missions of the United States in Ukraine or with any other purpose, if the period of their stay in Ukraine is more than 90 days, visas are required.
1. Passport must be valid 3 months beyond intended stay
2. Tickets and Documents for return or onward travel
3. Visa is Required
4. Vaccination - None Required
Requrements For Foreign Citizens To Obtain Visa To Ukraine
1. Passport must have at least six months remaining validity
2. Application form fully completed and signed
3. Passport-type photograph