Australia to join US in Gulf maritime security mission.

Australia Navy will join the US-led mission to protect shipping through the Strait of Hormuz amid heightened tensions with Iran, Prime Minister Scott Morrison announced Wednesday.

The US Navy is already keeping watch on the Strait of Hormuz and trying to build a coalition of partners to help (Picture source: AFP Photo)

"This destabilising behaviour is a threat to Australia’s interests in the region," Mr Morrison told a news conference in Canberra.

"The government has decided that it is in Australia’s national interest to work with our international partners to contribute. Our contribution will be limited in scope and it will be time-bound," he said.

Mr Morrison said Australia will send a P-8A Poseidon surveillance plane to the Middle East for one month before the end of 2019, while an Australian frigate will be deployed in January 2020 for six months.

Additionally, Australia will provide support staff to the mission, which will also involve British forces.

Defence Minister Linda Reynolds said Australian military staff would in coming weeks join the security operation’s headquarters in Bahrain, which announced its involvement in the operation on Tuesday.

Australia’s deployment will expand US-led efforts to secure the strait, which lies between Oman and Iran and through which almost a fifth of the world’s oil passes after tensions spiked between Iran and Britain.

US Secretary of State Mike Pompeo and Defence Secretary Mark Esper had requested Australia's help patrolling the strategic waterway during a visit to Sydney earlier this month.

The move follows a spate of incidents - including the seizure of ships - involving Iran and Western powers, in particular, Britain and the US, centred on the vital Gulf channel.

However, European countries, which disagree with a US decision to impose sanctions on Iran, have been reluctant to sign up to a US-led mission for fear of adding to the tension in the region.