The United States has suddenly decided to re-engage with this region.

It has certainly blown hot and cold in the past, and even staunch allies in Southeast Asia have felt the icy chill of neglect, as they did under former President George W Bush.

His administration stiffed this region most crudely in 2005 when then Secretary of State Condoleezza Rice declined to attend the ASEAN Regional Forum in Vientiane that year.

It may sound like small beans, but at the time it was a thunderbolt, since all Rice’s predecessors – Colin Powell, Madeleine Albright, Christopher Warren – had always attended.

Being stationed in Washington at the time, I remember the angry chorus of complaints from Asian diplomats that the US was ignoring ASEAN, and that China would move into the vacuum.

Well, it certainly did. And it appears to have taken until now for the US to fully realise this and to start doing something about it.

Under its new stand-up-to-China campaign, Washington is urging countries such as Vietnam and its neighbours to unite in balancing Beijing’s increasing assertiveness.

The campaign began in earnest at last month’s ARF in Hanoi, where Rice’s successor, Hillary Clinton, walked tall and carried a big stick.

Catching Beijing completely off guard, Clinton announced that the US would inject itself into the volatile sovereignty disputes in the South China Sea.

The key dispute is between China and Vietnam. Both claim a huge area of the sea, including the Paracel and Spratly Islands, which are rich in fish stocks and deposits of oil and gas.

Naturally, China reacted to Clinton’s statement with unrestrained fury, since it amounted to supporting Vietnam, which throughout history has regarded China as a traditional enemy.

Then, last week, the US dropped another bombshell by revealing that it was close to signing an accord with Hanoi to share nuclear fuel and technology with Vietnam.

Under the new arrangement, Hanoi will even be allowed to enrich uranium on its own soil – uranium that could theoretically be used in nuclear

weapons.

Li Qinggong at the China Council for National Security Policy Studies said that the nuclear talks show the US is “strengthening cooperation with Vietnam to contain China”.

He is absolutely right. And it is a very dangerous development. We may be entering a new nuclear Cold War between the US and China, and its battlefield could well be Southeast Asia.

Roger Mitton is a former senior correspondent for Asiaweek and former bureau chief in Washington and Hanoi for The Straits Times.