If you were previously denied a visa
If you were refused a visa in Dhahran or Riyadh within the last year, you cannot re-apply in Jeddah.
Section 214(b) of US Immigration and Nationality Act states that "every alien shall be presumed to be an intending immigrant until s/he establishes to the satisfaction of the consular officer, at the time of application for admission, that he is entitled to non-immigrant staus..." Failure to overcome the presumption of intending immigrant is the most common reason for denial of a visa.
Applicants may re-apply for a non-immigrant visa at the post where they were previously denied. Such applicants must provide all documents again at the time of re-interview and must explain how their circumstances have dramatically changed since the previous interview.