Meeting in London today and tomorrow, the financial leaders of the G-20 nations will lay the groundwork for the Pittsburgh summit with talks on financial regulation, stimulus timetables and the shape of a post-crisis world economy.

The session comes as some of the world's larger economies are showing glimmers of growth, while others have yet to turn the corner. The mixed picture compounds the difficulty of turning the cooperative rhetoric of recent G-20 meetings into concrete actions to prevent the kind of market meltdown that has hobbled the world over much of the last two years.

"This is a stock-taking meeting, not a new-initiatives, new-agreement meeting," Treasury Secretary Tim Geithner said in Washington before heading to the London session. "We've come a long way," he said, according to a transcript of his pre-summit briefing. "But I think we have to be realistic that we've got a long way to go still."

He referred to the pace of economic recovery, but the nations that will meet in Pittsburgh have considerable policy distance to travel before they can coalesce behind the new regulatory structures that various world leaders have proposed in concept but not yet in precise detail.

Mr. Geithner told reporters that he would be urging his counterparts to consider steps including greater capital requirements for financial institutions. The pre-meeting rhetoric from some European countries, particularly France and Germany, have placed more emphasis on restrictions on bankers' bonuses in the belief that the industry's compensation practices encouraged the kind of reckless risk-taking that led the world to the brink of an economic abyss.

The leaders of France, Germany and Great Britain issued a joint letter this week, which emphasized their common ground on several of the key issues that will confront the London and Pittsburgh meetings. Earlier in the year, there had been a broad perception that the UK, the United States and China were champions of a more aggressive approach to government stimulus spending than their partners in continental Europe. At the same time, French and German officials were more aggressive in proposing curbs on compensation in the financial sector.

The joint letter from the Europeans suggested a common resolve on continuing to pursue stimulative policies, while enlisting Britain's Prime Minister Gordon Brown in support of the compensation curbs that French President Nicolas Sarkozy and German Chancellor Angela Merkel had called for in a meeting in Berlin on Monday.

In his pre-summit remarks, Mr. Geithner also described compensation rules as "a critical part of the reform agenda."

The U.S. House has also moved to restrict bankers' bonuses. But some experts are skeptical of the changes of creating structures to implement such rhetoric across national borders.

"It's interesting that a real split has opened up," said Lee Branstetter, a professor of economics and public policy at Carnegie Mellon University. "On the one hand, Germany and France are focusing on pay, on the other side, Britain the U.S. and to some extent Japan are suggesting that government intervention, however well intentioned, could have unforeseen costs and limited benefits."

He added that agreement on the process was likely to be as elusive as a consensus on the substance of the regulatory goals.

"Traditionally, financial market regulation is a prerogative of national governments," he said. "I would foresee a lot of reluctance by national governments to surrender that power. I would be surprised if there's any strong resolution reached on this matter in either London or Pittsburgh."

Similar hurdles are likely for Mr. Geithner's suggestions about new capital requirements and transparency rules.

"A critical priority for us is going to be ... to try to make sure that you are seeing enough progress at a sufficiently ambitious level across the major financial centers so we're left with a more conservative set of standards applied more evenly, more uniformly, around the world," he said.

Mr. Geithner emphasized that the conversation at this point was a preliminary assessment "about a framework of design principles." But he emphasized the need for urgency.

"This is not something we can take a long time to do," he said. "It took the world a very long time to reform the previous system and that was a consequential and very costly failure of cooperation and we're not going to repeat that mistake."

The suggestion of stabilization in some economies is also expected to further debate on when the major economies should make major course changes on their stimulus packages.

"Already, there are calls form Germany that it's time to start winding up the global stimulus, and the position of the U.S. and Britain is, 'not yet,' " said Mr. Branstetter, who is also an associate editor of the Journal of International Economics.

Any number of other policy challenges await the finance and treasury officials this weekend and in subsequent talks. Chief among them are efforts to spur movement in two sets of long-stalled global negotiations -- the talks on a post-Kyoto climate change accord, scheduled for later this year in Copenhagen, and the overall international trade talks known as the Doha Round.