Australia's prime minister has defended the leasing of a strategically important port to a Chinese company, saying the military could seize control in a crisis.

Prime Minister Malcolm Turnbull told reporters in the Philippines on Thursday that Australian defense officials were not concerned by the deal and had not lost control over Darwin city's port.

The Northern Territory government has struck a deal to lease the port to the Chinese government-linked Landbridge Group for 99 years.

The deal has attracted criticism because Darwin in an important military base on the northern Australian coast, where up to 2,500 U.S. Marines train as part of increasing U.S. defense resources in the Asia-Pacific region.

President Barack Obama raised the deal in discussions with Turnbull at an Asia-Pacific Economic Cooperation summit in the Philippines.