Long viewed as big on talk but short on action, a bloc of Southeast Asian nations has seen its global clout surge during the last year under the leadership of regional giant Indonesia. But the group’s impact could diminish after the torch passes to smaller, less democratic nations following a summit this week.

That would be bad news for the United States, which has looked to the Association of Southeast Asian Nations to help keep China’s regional ambitions in check and to develop export markets for American businesses

Indonesia marks the end of its year as the bloc’s rotating chair by hosting the East Asia Summit, ASEAN’s annual get-together with leaders of regional powers including China, India and Japan. For the first time the presidents of the US and Russia also will attend.

Next year, the ASEAN chair and summit host will be Cambodia, to be followed in subsequent years by Brunei, then probably Myanmar and Laos. All but one of those nations, the tiny oil sultanate of Brunei, count China as a chief ally and have fragile relations with Washington.

The US has championed the activism of Indonesia, Southeast Asia’s most powerful nation and strongest democracy, during its tenure. Indonesia has mediated in a bloody Thai-Cambodia border dispute and nudged military-run Myanmar, also known as Burma, toward reform.

As well as overcoming ASEAN’s traditional resistance to wading into the affairs of its 10 members, Indonesia has pushed the grouping toward greater global recognition. At this week’s summit held in Bali, it will be urging world powers to keep Southeast Asia free of nuclear weapons.

It is doubtful whether the smaller nations, with less diplomatic clout and, in some eyes, questionable legitimacy at home, can show the same initiative.

Cambodia, whose leader Hun Sen staged a violent coup against his own co-prime minister 14 years ago, takes over in 2012. The chair then passes to Brunei in 2013, before it is expected to be handed in 2014 to a pariah state edging toward international rehabilitation, Myanmar. The communist government in Laos takes over in 2015.

ASEAN takes decisions by consensus, limiting what any single member nation can achieve, but the chair has the important roles of hosting meetings and setting the group’s agenda in consultation with the other nine countries. It will need a strong direction if it is to achieve by 2015 its goal of an ASEAN Community, a kind of European Union-lite, which would deepen regional cooperation on issues ranging from good governance and human rights to security and conflict resolution.

The US supports such integration, hoping ASEAN can fill a void in the kind of institutional structures for regional cooperation that Europe has in the form of the EU and NATO.

Before Indonesia’s stint, Vietnam as chair in 2010 led a diplomatic drive to counter China’s assertive claims to sovereignty over the South China Sea, amid growing unease in the region about Beijing’s growing military might. The US weighed in, saying it had a national security interest in peaceful resolution of territorial disputes that China has in those waters with Vietnam, the Philippines, Malaysia, Brunei and Taiwan.

Secretary of State Hillary Rodham Clinton reinforced the message Wednesday, signing a declaration with the Philippines calling for multilateral talks to resolve maritime disputes.

The United States wants to reassert its status as a Pacific power, and by going to Bali, President Barack Obama is signaling his administration’s growing attention to the region as it winds down its involvement in the wars in Afghanistan and Iraq.

The strategy aims at both building trade ties and consolidating the US role in underwriting security in the Asia-Pacific since World War II. The US wants to deepen its military presence and announced Wednesday new troop deployments in Australia to begin next year.

US allies and even a former foe, Vietnam, have encouraged increased US engagement. But ASEAN’s members, even US treaty allies like the Philippines and Thailand, do not want to pin their allegiances solely to either Washington or Beijing.

ASEAN walks a delicate diplomatic line between the world powers, and in terms of trade. ASEAN has opened its markets faster with China than the US, having established a regional free trade zone in 2010.

The impoverished economies of Cambodia, Laos and Myanmar, however, long have been seen as aligned with China, a major source of investment and military hardware. As nonclaimant states in the South China Sea, they are unlikely to take a strong stand on an issue on which China would prefer no ASEAN or US involvement.

There are limits on that allegiance, however, as the rest of ASEAN is not going to put up with a pro-China agenda. The three nations may also be conscious of becoming over-dependent on China and want to improve their ties with the United States.

Washington has in particular been courting Myanmar’s government as it begins opening up from half a century of military dominance, moves that could help end its international isolation and smooth the way for it to hold the ASEAN chair in 2014.

Myanmar recently stopped work on a massive China-built dam project. That curried popular favour at home but also showed it does not want to be seen as a client state of Beijing.