Over the past 3 years, Asia has steadily climbed up US President Barack Obama’s list of priorities. However, the administration has been very reluctant to clearly state why this shift is taking place. What makes this gradual transition so complicated? Put simply, the answer is China. The US must prepare for the military and strategic challenges posed by the Chinese –but they have help. Despite its lackluster performance in the Olympics, Australia is at least going for gold when it comes to assisting the US to ensure its preparedness in Asia. Thanks to increased assertiveness by Beijing – including expanding its stock of submarines and ballistic missiles – Australia has stepped up as a strategically valuable partner.The writer is a commentator who divides his time between the United Kingdom and Southern California. He has appeared on CNN, CNBC, BBC and Sky News, and has been featured in the New York Times, the Wall Street Journal, the Washington Post, the Financial Times and the Economist.According to US Defense Secretary Leon Panetta, Australia is now America’s “most important ally.”The US Marines currently training in the harsh conditions of the outback are part of President Obama’s plan for an increased military presence across South East Asia in an effort to check Chinese ambitions in the region. The Obama administration is also courting the Philippines, Thailand, and Vietnam.Australia, though, remains central to Obama’s strategy. Current plans have the number of US marines stationed in Australia increasing to 2,500 over the next five years. What began as a limited deployment to the far north city of Darwin could eventually evolve to include larger scale cooperation, such as upgrading Australian naval bases to accommodate US ships or even locating B52 bombers on Australian airbases.However, Australia must be wary of Beijing’s anger – China is one of their most important trading partners. As a result, Canberra must walk a treacherous tightrope between its economic need for good commercial relations with China and its strategic need for a Chinese foreign policy that does not destabilize the region. While the current marine deployment can be discussed in neutral terms – such as enabling a rapid response for natural disasters – there are red lines which Australia is unwilling to cross. A proposal last week for a US aircraft carrier detachment to be stationed permanently at the Stirling Naval Base in Western Australia was roundly rejected by Australian Defense Minister Stephen Smith.Despite a strong desire to support the US' efforts in Asia, Canberra fears that allowing US military bases in Australia would be a step too far for Beijing. “Joint training” is one thing, assertive displays of US military hardware, of course, is another thing all together.The risks for conflict in Asia are real. For example, Beijing has become increasingly assertive with its territorial claims. As a result, China is frequently coming into conflict with neighbors, like Japan and Taiwan, as well as Southeast Asian countries like Brunei, Malaysia, and the Philippines. Strategically located, the South China Sea has been squabbled over by rival claimants for decades. Some experts even believe it may contain oil deposits that have yet to be discovered.It is not difficult to imagine one of these flag-waving standoffs eventually degenerating into an actual conflict that results in a loss of life and a potential escalation thereafter.In addition to military engagement, Washington is also backing local diplomatic efforts, including those of the Association of Southeast Asian Nations (ASEAN), which coordinates the affairs of the smaller countries in the region. Some ASEAN members are more conciliatory towards Beijing, while others continue to spar. Unfortunately, both sides are annexing various uninhabited rocks as new “provinces,” laying the groundwork for future claims and conflicts.Meanwhile, China has been strengthening ties with its closest allies. This week, North Korean leader Kim Jong-un held the first diplomatic talks of his short time in power with a group of senior Chinese officials in Pyongyang. The younger Kim is clearly trying to differentiate himself from his father, Kim Jong-Il, who was notoriously reluctant to step into the spotlight.North Korea depends on China for its existence and ambitions – however modest or grandiose they may be. At a time when the United Nations is reporting that two-thirds of North Koreans are suffering severe food shortages, Kim will need all the friends he can get and China is a good place to start.The de-militarized zone between North and South Korea remains a potential flashpoint for international conflict. Although the US has no direct claims in the region, it has a significant interest in the continued peace and prosperity of Asia, including China. China is currently undergoing a generational transfer of power among the upper echelons of its government, and as a result deserves Washington’s full attention. US marines can expect to remain residents of Robertson Barracks – an Australian army base just outside of Darwin – for some time to come. An ongoing American military presence in Okinawa, Japan was also a key element in US preparation during the Cold War with the Soviet Union. As China continues to grow in importance and influence in the coming decades, US policy in the region is evolving to reflect the updated realities on the ground.The Obama administration must have the foresight and dexterity to ensure that its partnership with Australia and increased commitment to the region fosters stability and peace instead of disruption and uncertainty.