Tourist and Business visas are not required for citizens of the United States for a stay up to 28 days. However, your passport must have at least one blank visa page and be valid for six months beyond your intended stay. If your passport is expiring or you need to have additional pages added you can view the requirements here.
If you intend to stay for longer than 28 days please see full visa requirements here
Fast Passports & Visas always recommends checking with your airline as requirements may change without notice.