Britain, France and Germany have vowed to clamp down countries that refuse to share taxation information with others and help tax evasion. The sanctions they want would include cutting investment, imposing taxes on funds held in tax havens and withdrawing development aid, Brown said in July.
Several countries — including Switzerland and Liechtenstein — have moved swiftly to increase how much tax information they swap with other authorities after the Organization for Economic Cooperation and Development put them on a "gray list" of tax havens that don't meet information exchange standards.
U.S. Treasury Secretary Timothy Geithner is using the meeting to push talks on a new international accord to increase banks' capital reserves.
The Obama administration's proposal would establish stronger international standards for the reserves banks are required to hold to cover potential loan losses. The U.S. wants to reach agreement on an accord by the end of 2010, with countries agreeing to implement the plan by the end of 2012.
Brazil, Russia, India and China — the so-called BRIC grouping — held their own mini-summit on Friday, calling for faster action on changes to give them a greater say in governance of financial markets.
The G-20 countries have agreed to review the leadership of institutions like the World Bank and IMF, which has received pledges of more money to help struggling countries. The IMF is customarily headed by a European and the World Bank by an American.
The BRIC quartet want a shift in voting power at both the IMF and World Bank in favor of developing countries.
The G-20 includes 19 countries: Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, Britain and the United States. The European Union, represented by its rotating presidency and the European Central Bank, is the 20th member.