37 CFR § 1.412 - The United States Receiving Office.
(a) The United States Patent and Trademark Office is a Receiving Office only for applicants who are residents or nationals of the United States of America.
(b) The Patent and Trademark Office, when acting as a Receiving Office, will be identified by the full title “United States Receiving Office” or by the abbreviation “RO/US.”
(c) The major functions of the Receiving Office include:
(3) Collecting and, when required, transmitting fees due for processing international applications (PCT Rule 14, 15, 16);
(4) Transmitting the record and search copies to the International Bureau and International Searching Authority, respectively (PCT Rules 22 and 23); and
(5) Determining compliance with applicable requirements of part 5 of this chapter.
(6) Reviewing and, unless prescriptions concerning national security prevent the application from being so transmitted (PCT Rule 19.4), transmitting the international application to the International Bureau for processing in its capacity as a Receiving Office:
(iii) Where there is agreement and authorization in accordance with PCT Rule 19.4(a)(iii).