It's the Pacific, stupid.

As President Barack Obama begins his second term in office, that is the watchword for US foreign policy as the weight of Washington's diplomatic interests shifts away from the Middle East towards the Pacific basin. The move is entirely practical as the region is not just a "strategic pivot", to use State Department terminology: most of the countries within its orbit are major trading partners and natural allies of the US.

But last week's regional tensions, especially the military stand-offs involving Chinese, Russian and Japanese forces over territorial claims, showed it is also a tinderbox. By realigning its diplomacy the US is in danger of going head-to-head with China, a nuclear power with its own ambition to seize ownership of the region. Russia, too, has territorial and economic claims in the Asia-Pacific region and a US diplomatic source claims: "For the first since the Cold War ended there is the potential for the kind of stand-offs that were commonplace in the 1970s."

Last week tensions resulted in a stand-off between Russian and Japanese warplanes after two Russian Su-27 strike aircraft violated Japanese airspace over the island of Rishiri in the country's north. Japanese scrambled four F-2 fighters.

Japan and South Korea are involved in a long-running confrontation over an island known in Japan as Takeshima and Korea as Dokdo. Moscow and Tokyo are at loggerheads over the Kurile islands and North Korea continues to embellish its noisy neighbour reputation by testing a long-range ballistic missile and preparing to illegally test a new nuclear weapon.

To counter these possible threats and reinforce its own position the US is not without firepower. More than 350,000 military personnel are deployed in the region and over half of US warships patrol the Pacific with major bases in Japan, the Philippines, South Korea, Malaysia, Thailand, the Marshall Islands, Guam and Wake.

A vivid reminder of US strength came last week during a huge exercise which involved naval ships and warplanes from the US, Japan and Australia operating from the Pacific island of Guam. Forces from New Zealand and the Philippines are due to join the exercise this week.

"The training is not against a specific country, like China," insists Lieutenant- General Masayuki Hironaka of the Japan Air Self-Defence Force.

"However, I think the fact that our alliance with the US and Australia is healthy is a strong message."