Two rangers were on foot Friday looking for the man in Great Smoky Mountains National Park, on the Tennessee-North Carolina border.
A park spokeswoman said the hiker used his cell phone to call 911 on Thursday afternoon. He spoke to dispatchers again Friday morning and said he was hunkering down at his location and might not be able to hike out.
Two rangers walked nine hours Thursday before taking shelter and were thought to be about 4 miles from the man late Friday morning.
Park officials were considering the possibility of an air rescue, once the man has been located.