By Kate McGeown
BBC News, Hanoi
When US President George Bush arrives in Vietnam on Friday for the annual Asia Pacific Economic Co-operation (Apec) forum, he will undoubtedly attract a huge amount of attention.
Two APEC members overshadow the others
But for many of the delegates he is due to meet, Mr Bush will not be the star attraction. That accolade is reserved for Chinese President Hu Jintao.
China's meteoric economic rise has gripped the world, forcing changes that are apparent in all the bloc's 21 members, especially in Asia.
"I don't think it would be an exaggeration to say that most Asian countries now look to China more than they look to the US," said Prof Zhuang Jianshong, from Shanghai's Jiaotong University.
"Especially as an economic entity, China is certainly the shadow covering the entire region," added Prof Robert Ross, from Boston College in the US.
As its name would suggest, Apec is primarily an economic forum - intended to promote trade liberalisation and economic growth - and it is in this arena that China has become particularly influential.
China is now the dominant trading partner for much of S E Asia
The Chinese delegation will be arriving at Apec fresh from successes in pushing forward a range of free trade agreements.
Beijing has recently made important steps towards a deal with the South East Asian bloc Asean, as well as signing a series of multilateral and bilateral agreements both inside and outside the Asian region.
According to Rosemary Foot, an international relations professor at Oxford University, China will be keen to use Apec as an opportunity to cement these deals and emphasise its good relations with the rest of Asia.
While the US has also signalled its enthusiasm for more economic agreements in the region - even including an Apec-wide free trade partnership - Washington has actually signed relatively few important deals in recent years, an agreement with Singapore being the only notable exception.
"The US is coming to Apec in a position of trying to play catch-up," said Prof Ross.
But while the Apec conference is ostensibly about trade, the political, diplomatic and security meetings held on its sidelines are often more important than the main forum itself.
And it is here that Washington is still clearly the main player.
In terms of international diplomacy, the US remains the "global power of the moment," according to Prof Foot - in part due to its superior defence capabilities and corresponding political clout.
China recently held a successful trade summit with African leaders
American naval resources easily surpass those of all other nations in the Asia-Pacific region, and Washington continues to shore up its supremacy by building partnerships with its regional allies.
It has recently worked with Singapore to provide facilities for an aircraft carrier, increased its military presence in the Philippines and, despite cut-backs, retains a substantial number of troops in South Korea and Japan.
"We haven't seen the development of Chinese defence strategies to anything like the same extent," said Prof Ross.
That is not to say, though, that China's role in the diplomatic arena is insubstantial.
In the most urgent crisis currently facing the region, North Korea's intransigence over its nuclear ambitions, China is playing a central part in trying to reach a peaceful settlement.
As the nearest thing North Korea has to an ally, China has been praised for bringing it back to the negotiating table for six-party talks.
These six-party talks look set to be focus of many of the bilateral discussions on the fringes of this year's Apec meeting.
It seems that, like it or not, Asia-Pacific nations will have to learn to accommodate two key powers in their midst.
Prof Ross believes that the main challenge facing these nations is choosing which heavyweight to back.
He cited South Korea as a good example of a nation currently caught between the two powers - struggling to try to accommodate the wishes of China while not angering Washington.
"It's very difficult for countries to be neutral. If you're a small country, you need to align yourself with a bigger power - and ultimately you have to choose which one," he said.
Prof Foot, though, believes that most Asian nations are not willing to make a choice between China and the US - and are therefore keen to put regional agreements in place in which all major players have a stake.
"The region wants the US involved as well as China, even if it doesn't agree with US foreign policy sometimes, because it doesn't want to be left to deal with a powerful China alone," she said.