(a) When a vessel arrives at an Atlantic or Pacific coast port from a foreign port or ports with residue cargo for delivery at a port or ports on the opposite coast or on the Great Lakes, or where such arrival is at a port on the Great Lakes, with residue cargo for delivery at a port or ports on the Atlantic or Pacific coasts, or both, and the master, owner, or agent is unable at that time to designate the specific port or ports of discharge of that residue cargo, the Cargo Declaration, Customs Form 1302, filed on entry in accordance with § 4.7(b) shall show such cargo as destined for “optional ports, Atlantic coast,” or “optional ports, Pacific coast,” or “optional ports, Great Lakes coast,” as the case may be. The traveling manifest shall be similarly noted. Upon arrival of the vessel at the first port on the next coast, the master, owner, or agent must designate the port or ports of discharge of residue cargo as required by section 431, Tariff Act of 1930.

(b) For this purpose, the master shall furnish with the other papers required upon entry a Cargo Declaration, Customs Form 1302 in original only of inward foreign cargo remaining on board for discharge at optional ports on that coast, and the Cargo Declaration, must designate the specific ports of intended discharge for that cargo. The traveling manifest shall be amended to agree with that Cargo Declaration so as to show the newly designated ports of discharge on that coast and shall be used to verify the abstract Cargo Declarations surrendered at subsequent ports on that coast.