Except as provided in paragraphs (2) and (3), the term “United States source gross transportation income” means any gross income which is transportation income (as defined in section
863
(c)(3)) to the extent such income is treated as from sources in the United States under section
863
(c)(2). To the extent provided in regulations, such term does not include any income of a kind to which an exemption under paragraph (1) or (2) of section
883
(a) would not apply.