The U.S. is gradually ramping up the number of Marines at a base outside Darwin as part of President Obama’s plan, announced in 2011, to rotate up to 2,500 there for six months every year. Washington is seeking more places where it can expand its military footprint in Asia without triggering a backlash.

Beijing has bristled over what it sees as Washington’s attempts to contain China’s rapid economic and military expansion. Territorial disputes between China and its neighbors have flared in recent years, prompting several countries, including U.S. allies such as India, Japan and Australia, to strengthen security ties.

While both the U.S. and Australia are reluctant to consider permanent bases, U.S. forces already use other Australian military facilities such as air bases in the country’s north—where some of the world’s biggest weapons training ranges are. Officials have also looked at a naval port near the western city of Perth, for use by ships ranging in size from aircraft carriers to submarines.