France will walk away from this week's G20 summit if its demands for stricter financial regulation are not met, the finance minister has told the BBC.
Christine Lagarde told Hardtalk that President Nicolas Sarkozy would not sign any agreement if he felt "the deliverables are not there".
Strengthening financial regulation will be one of the key issues at the G20.
France wants a stronger global financial regulator than the US and the UK would like.
If France were to leave the summit, it would be a blow to both UK Prime Minister Gordon Brown and US President Barack Obama.
Both men have spoken of their high hopes for the meeting to stimulate international recovery.
"Leaders meeting in London must supply the oxygen of confidence to today's global economy and give people in all of our countries renewed hope for the future," Mr Brown said.
President Obama is due to arrive in London for the summit later. It will be his first visit to Europe since he became president.
The prime minister also called for the "values that we celebrate in everyday life" to be brought to the financial markets.
"I believe that unsupervised globalisation of our financial markets did not only cross national boundaries, it crossed moral boundaries too," Mr Brown said.
He was speaking at a gathering of religious leaders in St Paul's Cathedral with the Australian Prime Minister Kevin Rudd.
Mr Rudd warned that the global economic crisis was having a devastating effect on developing countries.
"This is the unseen cost of the crisis, the invisible face of the global recession," he said.
"But in conscience and for people of conscience we cannot stand idly by."
However, splits among other world leaders on how to tackle the economic crisis have also begun to emerge in other areas.
European countries, in particular, are resisting calls to commit to spending more this year and next.
President Sarkozy has previously spoken out against "Anglo-Saxon" economies, as has the prime minister of Luxembourg, Jean-Claude Juncker.
"This crisis started in the United States. The Anglo-Saxon world has always refused to add the dose of regulation which financial markets, the international financial system needed," Mr Juncker said last week.
The European Commission President, Jose Manuel Barroso, denied that there were any splits within the EU itself.
"In the last European summit we have agreed on a common position, a very ambitious position," he told the BBC.
"I will be happy if I see all our partners with the same level of ambition."
However, there have also been expressions of optimism.
German Chancellor Angela Merkel is reported to have said that chances were high that agreements - for example, to regulate hedge funds - would be reached.
And in spite of her walkout threat, Ms Lagarde was eager to stress that the G20 leaders agree on a range of important issues.
"I am absolutely determined, and President Sarkozy has said it loud and clear, that we actually eradicate non-cooperative centres and tax havens," she said.
"I know that Chancellor Merkel is very much on that line, I know that Gordon Brown has said that old tax havens have nothing to do with this new world.
"Well, we need to deliver on that and we need to be extremely united and strong."
G20 LONDON SUMMIT
World leaders will meet later this week in London to discuss measures to tackle the downturn. See to the G20 summit. The G20 countries are Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, the UK, the US and the EU.
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Published: 2009/03/31 14:48:42 GMT