French President Nicolas Sarkozy said on Wednesday it will be difficult for the London G20 summit to implement all the reforms needed to overhaul the financial system and added that further meetings might be necessary.
In a commentary to be published in several newspapers, Sarkozy said that although leading economies had made "gigantic efforts" in responding to the economic crisis, much work was still needed to prevent other such disasters.
"I am fully aware that we cannot achieve radical change overnight, that there is still a long way to go and that there may well be a need for other meetings, after London, in order to implement the reforms undertaken," he wrote.
World leaders will hold talks in London to discuss the economic meltdown on April 2 and Sarkozy has reportedly threatened to quit the meeting if his demands are not met.
Officials in Paris have laughed off the possibility of a walkout and there were no threats in Sarkozy's commentary.
Instead he repeated that he wanted to see "practical results" in London.
"Failure is not an option, the world would not understand it and history would not forgive us for it," he said.
Sarkozy insisted on the need for more action against tax havens, with France pushing for countries to be named and shamed if they failed to bow to pressure on ending bank secrecy.
"I want us to (adopt) a resolution which clearly identifies these tax havens and sets out in detail both the changes we expect them to introduce and the consequences which will ensue, should they fail to respond accordingly," he said.
However, some G20 officials have indicated this is unlikely to happen in London, with a few countries adamantly opposed to releasing any such lists.
Sarkozy said there had also been less progress in another area he thought important -- reform of accountancy standards and levels of oversight for financial firms.
"The current regulations failed to prevent abuses. They even made the crisis worse. I shall be putting this aspect to the fore, since sadly in many countries it has not been getting the attention it deserves," said Sarkozy.
The French president is due to hold talks with his Brazilian counterpart Luiz Inacio Lula Da Silva later on Wednesday in Paris before heading to London, where he is scheduled to hold a joint news conference with German Chancellor Angela Merkel.
Germany and France have worked hand-in-hand in preparing for this summit and will present a united face in London.
Officials in Paris said the two countries had achieved a lot in the build up to the meeting, including resisting pressure from the United States to spend more to revive their own economies.
Sarkozy said in his commentary that the full impact of the various stimulus packages was only starting to be felt, and promised to do more if it proved necessary.
"This is the principle I will be defending in London: to do everything necessary for world growth," he said.