By Andrew Walker
Economics correspondent, BBC World Service, Washington
Sixty-four years ago at a conference in Bretton Woods, New Hampshire, the foundations for post-war international finance were laid.
The G20 says there must be a global solution to current problems
Ahead of the G20 summit, some commentators have wondering whether we are going to see a new Bretton Woods.
It's ambitious talk. It is not likely that a single summit will deliver anything so grandiose, especially an event hosted by a US president who almost has his coat on, ready to leave the White House for the last time.
But there is clearly a desire among political leaders from these leading economies to do something - or, some might say more cynically, to be seen to do something - about the financial crisis that has suddenly engulfed them all.
And it really has hit them, from different angles and with different degrees of severity. A short global tour of a few G20 countries will give a flavour of why they are so concerned. (Incidentally, it's 19 countries, plus the European Union.)
The host, the US, is the main source of the financial poison - $1.4 trillion of it, according to the International Monetary Fund.
That is their latest estimate of the likely losses that will eventually be due to bad debts owed by American borrowers. Most of that is down to mortgages and financial securities based on them.
Brazil's financial markets have been caught in the side winds of the crisis. The stock market has fallen by more than half since May.
Russia has caught a bad case of the same contagion, aggravated by a problem it shares with Saudi Arabia: a falling oil price. Crude has come down by 60% from the highs it reached in July.
Brazil and other emerging nations have been hit by contagion
It is a result of the damage the credit crisis has done to the global economic outlook and so to demand for fuel. The developed countries are using less oil than last year.
China, Japan and Germany rely on exports for part of their economic growth. Anxious consumers in the US and other developed nations are already cutting back.
They are likely to do more of the same as credit gets harder to come by and concerns about job security mount.
Japan's economy has contracted, and China's prodigious growth has come off the boil.
That in turn is bad news for recession-hit Germany, whose exports include capital goods, such as factory machinery, to China.
So they all care about the problem. But what can they do?
There are two big issues: putting the immediate fire out and making the global economy safer in the future.
Fighting the blaze
The fire hoses are already at work. Indeed, they have been for more than a year.
Central banks have cut interest rates and been increasingly innovative in the ways they have provided loans to the banks and, in some cases, to other types of business.
The banking rescues, hastily put together last month, are another part of the effort.
Governments have also made a start on plans to use tax cuts and public spending as a stimulus to economies.
Hungary has called on the IMF for a bail-out package
That will be a big theme at the summit and a call for more of this fiscal stimulus is likely to be a central element of the advice the IMF will offer.
Further cuts in interest rates are also likely to be on the menu, with some economists saying the European Central Bank particularly needs to get moving more quickly.
Along with providing advice, the IMF's other key role is providing rescue loans. After several quiet years, the IMF is very much back in business.
Already packages are in hand for Iceland, Hungary and Ukraine. The IMF has a total of about $250bn it could lend. But will that be enough?
Some economists think not, if a few large emerging market countries need help.
British Prime Minister Gordon Brown wants the IMF's resources increased, perhaps with the oil producers and China making substantial contributions.
Of course, the IMF has a poor reputation in some countries, especially in Asia and Latin America. So agreeing an enhanced role for it won't be straightforward.
The fire next time
What about improved fire precautions for the future? That's perhaps less urgent. After all, what bank with badly burnt fingers is going to take crazy risks now?
But it is important nonetheless. Financial regulation is the big theme.
Restraints on bank lending, reform of credit rating agencies, how to supervise giant financial institutions - they are all big technically complex issues that will come under the microscope, probably in the follow-up to the summit.
The original Bretton Woods deal created financial stability with a system of fixed exchange rates. That part of the edifice collapsed in the early 1970s.
It won't be rebuilt this weekend. But there have been some calls for more managed currency policies. There is certainly an appetite in the US to talk about China's approach, which is seen as giving Chinese business an unfair competitive advantage.
So there are plenty of ideas around - for rapid economic stimulus, financial reform and a bigger war chest for the IMF.
But many ideas are controversial and some involve treading on the very sensitive toes of national sovereignty.
Just think how hard it can be to get anything done in the European Union or the World Trade Organization. A new world financial order would be every bit as hard to build.