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. More...