Sikkerhetssamarbeidet med Australia er av langt større betydning enn antall soldater skulle tilsi. Ikke minst Australias naboer ser med tilfredshet på at USA engasjerer seg.

Beskjedne 250 soldater skal utplasserer i Darwin, økende til 2500 US Marines, og de skal ikke bygge egne baser, men benytte australske. Med tiden kommer også luftvåpenet på plass.

Dermed kan USA projisere makt i en region som føler seg truet av Kinas økende makt. Regionen savner en motvekt, og den er det kun USA som kan levere.

Like Australia, China’s neighbors in Southeast Asia have looked to the United States to increase its military presence as a counterweight to Beijing. Mr. Obama has sought to provide that assurance, but the Asia-Pacific allies are well aware of the intense pressure for budget-cutting in Washington, and fear that squeezed military spending and other factors may inhibit Mr. Obama’s ability to follow through.

The United States and other Pacific Rim nations are also negotiating for a free-trade bloc that does not include China, the Trans-Pacific Partnership. The tentative trade agreement was a topic over the weekend in Honolulu, where Mr. Obama hosted the annual Asia-Pacific Economic Cooperation forum, and it will be discussed again later this week when he becomes the first American president to participate in the East Asia Summit, on Indonesia’s island of Bali.

For China, the week’s developments could suggest both an economic and military encirclement. For the United States and its Pacific Rim allies, they suggest a growing concern over China’s muscle.

But Mr. Obama said, “The notion that we fear China is mistaken. The notion that we are looking to exclude China is mistaken.”

The president said China would be welcomed into the tentative Trans-Pacific Partnership — nine nations, including the United States, agreed in Honolulu to finalize a framework in 2012 — if it is willing to meet the free-trade standards for membership. Such standards would require China to let its currency rise in value, better protect foreign producers’ intellectual property rights and limit or end subsidies to state-owned companies.

Det store spørsmål er hvordan Kina vurderer USAs avtale med Australia og hvordan Kina kommer til å reagere.

Eyeing China, U.S. Expands Military Ties to Australia