But no, Hugh White, it’s not only about China.

From the AUSMIN Meeting joint statement.

We recognised the growing importance of India in the region and the Indian Ocean’s importance to trade, maritime security, and strategic and defence planning.

We discussed progress in implementing the US force posture initiatives in Australia announced by Prime Minister Gillard and President Obama in 2011. We welcomed the success of the first rotation of US Marine Corps personnel to northern Australia, and looked forward to the next rotation in 2013. We discussed our enhanced aircraft cooperation, which is expected to result in increased rotations of US aircraft through northern Australia.

This deepening of our defence cooperation through these initiatives is a natural evolution of our existing, long-standing cooperation and is aimed at supporting long-term peace and stability in the Asia Pacific. These initiatives will improve Australian and US military capabilities through combined training and exercises, enhance our ability to respond to regional challenges, including humanitarian assistance and disaster relief, and provide a means of strengthening our cooperation with other regional partners.

We also discussed potential opportunities for additional naval cooperation at a range of locations, including HMAS Stirling. All of these possible areas of cooperation would require substantial further study and additional decisions by both capitals.

The communique notes: the US and Australia intend to “continue exploring opportunities for cooperation on Indian Ocean security matters.”

Rather than a crude blocking action against China, the move by the US would also be a shift to gain easier access to the Indian Ocean, where not only Chinese ships move but a rising share of the world’s commerce flows.

Incidentally, a number of governments in the region around WA including Indonesia and Malaysia are said to either not oppose a US naval presence or to quietly support it.