NEW DELHI - THE year 2012 began with festering Chinese sovereignty claims in the South and East China Seas, but also with hope that a code of conduct brokered by the Association of Southeast Asian Nations would enable them to be resolved peacefully. The year is ending, however, with those hopes dashed and Asean more divided than it has ever been. Indeed, a handful of its members now seem eager to subordinate their national interests - and the interests of Asean - to those of China.

China's increasing assertiveness in staking its claims contributed to the landslide victory of the defence-minded Liberal Democrats in Japan, and to the conservative Park Geun-Hye's election as South Korea's first-ever female president. Rising regional tensions also provided the backdrop to US President Barack Obama's trip to Southeast Asia shortly after his re-election.

Obama announced the United States' strategic "pivot" to the Asia-Pacific region in January 2012, and a whirlwind of activity there - from Australia to Indonesia to India - marked America's security diplomacy throughout the year. In Japan, too, worries about Chinese assertiveness have become so powerful that a government that showed considerable hostility to the US-Japan alliance when it came to power three years ago had, by November, begun to trumpet the alliance's mutual-defence commitments as it confronted China's claim to the Senkaku (Diaoyu) Islands.

The security concerns that have animated this diplomacy are forging a broad coalition, bringing in not only the region's democracies, but also countries like Vietnam, which is embroiled in its own territorial dispute with China that centers on maritime oil exploration. Even India, which has been cautious about deepening its security ties with the US, has now embraced the idea of regional mutual defence - not only with America, but also with Japan and other East Asian countries.

This new emphasis on regional security is not confined to governments. Popular support for the creation of a pan-Asian security structure can be found not only in the election outcomes in Japan and South Korea, but also in the ecstatic crowds that greeted Obama in Myanmar (Burma) during his recent tour. Ordinary Burmese well understand that their country's democratic transition is the direct result of its recoil from China's excessive demands on its natural resources.

So far, China's reaction to all of this new activity has been to dig in its heels and insist on addressing its territorial disputes with Asean's militarily inferior members on a bilateral basis. In November, China foiled Asean members' efforts to create a multilateral forum and an agreed code of conduct to govern economic and security activity in the South China Sea. By doing so, it split the group and may well have thwarted Asean's ambition to transform itself into a European Union-like regional bloc by the end of 2015.

China succeeded by winning over Cambodian Prime Minister Hun Sen, the host of November's Asean summit, who cut off discussion of China's assertive role in the South China Sea by falsely claiming that Asean's members had reached a "consensus" against "internationalising" the issue. (Ironically, in 1984, when Hun Sen was Foreign Minister, the ministry published a book entitled The Chinese Rulers' Crimes against Kampuchea, which documented China's backing for the genocidal Khmer Rouge.)

That Asean debacle has had serious consequences. The foreign minister of the Philippines, which is also currently engaged in a heated territorial conflict with China, called on Japan to rearm itself to balance China militarily, notwithstanding his country's bitter legacy of Japanese occupation. The landslide election of Shinzo Abe, who campaigned on a robust defence platform, may well lead to a serious Japanese push to invigorate the country's military capabilities.

A recent announcement by the provincial government in Hainan, China, which has responsibility for the South China Sea territories claimed by China, has probably reinforced that impulse. According to the Hainan authorities, from January 1, 2013, China's police will be authorised to board and detain ships that are suspected of "illegal activities" in what China claims are its territorial waters.

What constitutes "illegal" activity in the eyes of the Hainan authorities was not spelled out, but many worry that the order will give carte blanche to the maritime police to interfere with commercial activity in the South China Sea. This approach, according to Stephanie Kleine-Ahlbrandt of the International Crisis Group, appears to be "part of an overall strategy by Beijing to more forcefully defend its sovereignty claims" by "operational means."

As a result of China's hardening stance, Surin Pitsuwan, Asean's outgoing secretary-general has said that Asia is entering its "most contentious" period in recent years. Indeed, he warns that "the South China Sea could evolve into another Palestine," unless countries try harder to defuse rather than inflame tensions.

One reason to hope that matters will not get out of hand is China's deep integration into the global economy. But, within China, as the American political scientists Andrew Nathan and Andrew Scobell argued recently in Foreign Affairs, there is growing tension between domestic economic priorities and Chinese leaders' belief that "China's political stability and territorial integrity are threatened by foreign actors and forces."

The fears of China's rulers, I suspect, do not bode well for reaching a peaceful resolution of its territorial disputes in the South and East China Seas. A country that is "unstable at the grass roots, dejected in the middle strata and out of control at the top," as a group of Chinese scholars recently put it, may see adventurism abroad as the best means of maintaining unity at home.

Jaswant Singh, a former Indian finance minister, foreign minister, and defence minister, is the author of Jinnah: India - Partition - Independence.