Distributions by United States to nonresident aliens
The amount includible under subsection (a) in the gross income of a nonresident alien with respect to a distribution made by the United States in respect of services performed by an employee of the United States shall not exceed an amount which bears the same ratio to the amount includible in gross income without regard to this paragraph as—
(A)#
the aggregate basic pay paid by the United States to such employee for such services, reduced by the amount of such basic pay which was not includible in gross income by reason of being from sources without the United States, bears to
(B)#
the aggregate basic pay paid by the United States to such employee for such services.
In the case of distributions under the civil service retirement laws, the term “basic pay” shall have the meaning provided in section 8331(3) of title 5 , United States Code.