The 4700-kilometre network is being partly funded by the federal government to bring high-speed internet to Papua New Guinea and the Solomon Islands.
Australia committed $136 million to the project in 2018 amid concerns about Chinese firm Huawei’s involvement in the project.
Cable laying ship, the Ile de Brehat, was set to complete landing of the cables in Tamarama on Sydney’s eastern beaches on Aug. 28.
This caps off more than 4,500km of cable laid between Port Moresby in Papua New Guinea, Honiara in Solomon Islands and Sydney, chief executive of telecommunications firm Vocus Kevin Russell said.
The sea cable will then be connected to an underground land cable which was installed earlier in August.
Once joined, the Ile de Brehat will connect the cable to the final splice point which is about 180km offshore.
The ship will return to Solomon Islands to lay a separate 730km submarine cable linking Honiara, the capital city of Solomon Islands, to the provincial island centres of Auki, Noro and Taro.
The project is due for completion by December.
Foreign Affairs Minister Marise Payne said the laying of the cables will increase the connectivity between and within Australia and its two Pacific neighbours “in a way that nothing else we contemplated could have”.
“It will without any exaggeration change lives in the delivery of government services, in the capacity to do business, in the capacity to connect with family within both Papua New Guinea and the Solomon Islands,” she told reporters in Sydney on Aug 28.
The World Bank has forecast improved internet access and connectivity could bring in more than $US5 billion ($A7.4 billion) to the economy of the Pacific region and create almost 300,000 new jobs by 2040.
By Heather McNab