Looming over a glass counter scattered with jade rings, the woman from Guangzhou finally reaches her decision: her fidgeting husband perks-up and begins noisy negotiations with the Hong Kong jeweller. A price is agreed, but instead of Hong Kong dollars, the deal is settled in mainland yuan.

Given the proximity of the border, there is nothing too surprising about the transaction, perhaps: for the sake of good business, three other jewellers along the same Hong Kong street cheerfully accept what are, never mind “one nation, two systems”, another nation’s banknotes.

But the casualness of the transaction raises a question which could first reshape the world of trade and later the geopolitical scene. It may be jade rings and tourists now, but when will deals for three million barrels per day of crude oil be fixed, not in dollars, but in the Chinese currency?

The immediate answer, probably, is that while such a day may still be some way off, it will arrive much sooner than New York, London and Tokyo would like to think. To become an international currency, the yuan would have to undergo a series of substantial technical alterations from its present status, not least becoming freely convertible like the dollar, euro, pound and yen.

For Beijing, there would be huge cost risks involved if the currency were suddenly flung to the full mercy of international markets. Such a calculated loss of control may simply prove intolerable to a government that knows no other way.

And yet three of the most vital ingredients for the yuan to become an international currency are quite visibly stewing away: opportunity, momentum and willpower.

The opportunity arises from the financial crisis and the certainty that whatever global regime emerges on the other side will be a rebalanced version of the old one — it is hard not to envisage that process favouring China and there are clear signs that it has begun to do so. Qu Hongbin, chief China economist at HSBC recently told The Times that efforts by Beijing to strengthen trade and investment links with the Middle East and Latin America “sets the stage for a new world trade order”.

Further, the crisis has provided scope for developing nations, especially ones dominated by commodity exports in South America and the Middle East, to unhitch their loyalties from the US at somewhat lower risk than before. The American and EU economies may be huge, but nearly all the growth in crude oil, iron ore, copper and coal demand is derived from the developing world, with China high atop the list.

A few weeks ago, Brazil’s president, Lula da Silva, suggested in an interview that as its biggest export destination, China should start denominating its trade with Brazil in yuan rather than US dollars. Ben Simpfendorfer, the chief China economist at Royal Bank of Scotland, believes we may be approaching a point where China offers trade credit in yuan to Middle Eastern oil exporters — countries that are, in any case, buying an increasing proportion of imports from China.

And the momentum is clear too. It remains a long step from allowing the currency to trade freely around the world, but Beijing has quietly begun a series of changes to the way the yuan is used, including the facility for extending yuan-denominated loans to nations with whom it trades, and allowing investors in Hong Kong to buy yuan-denominated bonds.

None of these, alone, makes the yuan anything like an international currency. But this is a pattern of behaviour that should be on the world’s political radars rather than just the charts of a few economists.

For, perhaps most critically, there is evident willpower: Beijing wants this to happen just as it surely wants its economy to overtake Japan’s and eventually mount an assault on the dominance of the US.

Within the Communist Party there will be wide divisions over policy and extreme caution on the issue, said Wengsheng Peng, Barclays Capital's chief China economist, but there is growing consensus that the yuan should, in principle, become an international currency. What may now be isolated deals in a Hong Kong jade shop could eventually be played out on the world’s biggest commodity markets. “Long term, the objective is very clear,” said Dr Peng.

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