Pakistani police arrested a 20-year-old American man in an area near the Afghan border where there are many Islamic militants.
Authorities said the man was arrested at a checkpoint while trying to enter a tribal area without the special permission required by Pakistani law.
One police officer said the man was wearing traditional Pakistani dress and appeared to be a civilian.
Pakistani authorities identified the man as Juddi Kenan. They said he told them he was a student at a community college in Florida.