Australia's new prime minister has questioned China's strategy in the disputed South China Sea in a broadcast interview.
China has been "pushing the envelope in the South China Sea", he told the Australian Broadcasting Corp.
China's recent land reclamation activity in the area has angered neighbours with competing claims and ratcheted up tensions in the region.
China is Australia's biggest trading partner.
Mr Turnbull, who was sworn in as prime minister last week, has yet to outline how he will balance Australia's longstanding diplomatic allegiance to the US against its economic ties to China.
He said China's actions, including the construction of military bases on reclaimed atolls, could draw neighbours closer to the United States.
"My own view and the government's view is that China would be better advised, in its own interests frankly, not to be pushing the envelope there and that is why there's been resistance against that activity.
"You would think what China would seek to achieve is to create a sufficient feeling of trust and confidence among its neighbours that they no longer felt the need to have the US fleet and a strong US presence in the western Pacific," he said.
Disputed islandsThe dispute in the South China Sea is over the sovereignty of ocean areas, and the Paracels and the Spratlys - two island chains claimed in whole or in part by a number of countries.
Alongside the fully fledged islands, there are dozens of rocky outcrops, atolls, sandbanks and reefs, such as the Scarborough Shoal.
Although largely uninhabited, the Paracels and the Spratlys may have reserves of natural resources around them.
The sea is also a major shipping route and home to fishing grounds that supply the livelihoods of people across the region.
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