Following the cancellation of the Australian light destroyer project in 1973, the British Type 42 destroyer and the American "Oliver Hazard Perry"-class frigate were identified as alternatives to replace the cancelled light destroyers and the "Daring"-class destroyers. Although the "Oliver Hazard Perry" class was still at the design stage, the difficulty of fitting the Type 42 with the SM-1 missile, and the success of the "Perth"-class acquisition (a derivative of the American "Charles F. Adams"-class destroyer) compared to equivalent British designs led the Australian government to approve the purchase of two US-built "Oliver Hazard Perry"-class frigates in 1976. A third ("Sydney") was ordered in 1977, followed by a fourth, with all four ships integrated into the USN's shipbuilding program. A further two ships were ordered in 1980, and were constructed in Australia.