Australia possesed just limited facilities for arming American merchant ships according to the U.S. Joint Intelligence Committee. Daily summary dated 8 January 1942

An item reported that Australia possessed limited facilities for arming a few American merchant ships and tankers with anti-submarine guns. The supply of guns was small and only possible in exceptional cases.

Source

Map Room Papers (Roosevelt Administration), 1942 - 1945. U.S. Joint Intelligence Committee. Daily summary No. 29 dated 8 January 1942