WORLD leaders are making final preparations for this week's G20 summit in Argentina on Friday and Saturday. The meeting, which is billed as the moment when US-China trade tensions could come to a head, may become the most important G20 since the 2009 meeting in London during the storm of the global financial crisis.

Presidents and prime ministers will be in attendance - from the United States, China, Germany, India, Japan (which will be the G20 president next year and host the event in Osaka), Indonesia, Australia, Russia, Brazil, United Kingdom, Saudi Arabia, South Africa, Turkey, France, Italy, Germany, Canada, South Korea, Argentina, Mexico and the EU. Collectively, these powers account for some 90 per cent of global GDP, 80 per cent of world trade and around 66 per cent of global population.

Last year's summit in Hamburg was most memorable for the divisions within the G20 powers, especially the United States and key EU countries, over issues such as international trade, migration and climate change. To be sure, there was not complete disagreement in these areas with all parties, for instance, acknowledging the importance of limiting global temperature rises to no more than two degrees Celsius above pre-industrial levels. However, given US President Donald Trump's rejection of the Paris Agreement, significant differences were aired over the means to secure this ambition and he ultimately was isolated 19-1 on this specific issue.

Another flashpoint was the collision between German Chancellor Angela Merkel's push for a strong G20 reaffirmation of international trade and the US president's victory in securing language in the end-of-summit communique that countries can protect their markets with "legitimate trade-defence instruments".

This same topic is also likely to be central to this year's meeting narrative with Beijing and Washington having been locked, now, for several months in what could descend into a trade war with Mr Trump already imposing tariffs of some US$250 billion, and China retaliating with some US$110 billion of duties. Last week, White House economic adviser Larry Kudlow said he foresaw a confrontation between Washington and Beijing at the G20 after a growing war of words following the Apec summit.

On Thursday, Mr Trump expressed optimism again that a breakthrough could potentially be reached with China before Jan 1 when a new round of US tariffs commences that will increase duties to 25 per cent on a broad range of consumer goods. Yet, for that to happen, he is clearly looking for more negotiating carrots from Beijing after he asserted earlier this month that a list of 142 concessions offered was "not acceptable".

The potentially escalating US-China spat comes at a difficult time for the international trading system with G20 countries applying around 40 new trade restrictive measures between May and October, covering around US$481 billion of trade, the World Trade Organization (WTO) said last week.

Three-quarters of the latest trade restrictions were tariff hikes, many of them retaliation to steel and aluminium tariffs imposed by Mr Trump in March. The new restrictions were the largest since the WTO started specifically monitoring G20 trade in 2012.

This data underlines that it is not just the US trade spat with China that has caused ructions in recent months, for Washington has also been in trade disputes with other key entities, including the EU, Canada and Japan.

And in this troubled context, one indicator of the summit's success will be in being able to break through these trade tensions and agree on an end-of-summit communique. All previous G20 sessions have done so, but in recent global summitry - including June's G7 in Canada and the Apec meeting earlier this month in Papua New Guinea - both saw unprecedented failures to agree communiques.

One other reason why the summit will be noteworthy is that it could help mark a symbolic reconciliation between Argentina and the United Kingdom some three-and-a-half decades after the 1982 Falkland Islands war. In attending the summit, Theresa May will become the first sitting UK prime minister to visit Buenos Aires since that conflict with both countries keen to build ties from trade to the environment.

The massive amount of attention on this year's G20 highlights, yet again, that the body is widely perceived since the 2008-09 financial crisis to have seized the mantle from the G7 as the premier forum for international economic cooperation and global economic governance. It is now a decade since the G20 was upgraded from a finance minister body to one where heads of state now meet too - a move which was greeted with considerable fanfare, including from then-French President Nicolas Sarkozy when he claimed that "the G20 foreshadows the planetary governance of the 21st century".

Yet, the fact is that the forum has failed so far to realise the full scale of the ambition some thrust upon it, at the height of the global financial crisis. A key part of failure to deliver on previous high expectations is that the G20 meetings have no formal mechanisms to ensure enforcement of agreements by world leaders.

Also lingering are concerns by states outside the G20 about the club's composition which was originally selected in the late-1990s by the United States along with G7 colleagues. While states were nominally selected according to criteria such as population, GDP and so on, criticism has been made of omissions such as Nigeria, sometimes called the "giant of Africa", which has three times South Africa's population.

Former Norwegian foreign minister Jonas Gahr Store has gone so far to call the G20 "one of the greatest setbacks since World War II" inasmuch as it undermines the United Nations' universal sense of multilateralism. Reflecting this, the UN General Assembly convened a rival UN Conference on the Global Economic Crisis in 2009 as an alternative forum.

Taken overall, while the G20 has not yet lived up to some of the initial expectations of it, it continues to be a forum prized by its members as the session in Argentina will show. This year's forum could be especially memorable given the possibility of Mr Trump and his Chinese counterpart Xi Jinping securing a breakthrough in US-China trade tensions.