The G-20 (more formally, the Group of Twenty Finance Ministers and Central Bank Governors) is a group of finance ministers and central bank governors from 20 economies: 19 of the world's largest national economies, plus the European Union (EU). It also met once at heads-of-government level, in November 2008. Collectively, the G-20 economies comprise 85% of global gross national product, 80% of world trade (including EU intra-trade) and two-thirds of the world population.

The G-20 is a forum for cooperation and consultation on matters pertaining to the international financial system. It studies, reviews, and promotes discussion among key industrial and emerging market countries of policy issues pertaining to the promotion of international financial stability, and seeks to address issues that go beyond the responsibilities of any one organization.

Members of G-20

Argentina    Australia    Brazil    Canada    China    France    Germany    India    Indonesia    Italy    Japan    Mexico    Russia    Saudi Arabia    South Africa    South Korea    Turkey    United Kingdom    United States

The 20th member is the European Union, which is represented by the rotating Council presidency and the European Central Bank.

In addition to these 20 members, the following forums and institutions, as represented by their respective chief executive officers, participate in meetings of the G-20:

• International Monetary Fund
• World Bank
• International Monetary and Financial Committee
• Development Committee of the IMF and World Bank

Leaders of the world's largest economies are close to an agreement to tackle the global financial crisis.

The International Monetary Fund, which helps struggling economies, is set to get up to $500bn (£340bn) more funding.

There may also be a deal to "name and shame" countries that breach free-trade rules, BBC business editor Robert Peston reports from the G20 summit.

There will be measures to open up tax havens. Tighter regulation of banking and bankers' pay is also expected.

Significantly, leaders will also agree changes that will in effect create $250bn of new money to stimulate the global economy.

They will substantially increase the currency reserves of poorer countries by expanding the so-called special drawing rights the IMF makes available to economies in trouble.

Key measures

Leaders started the day with a working breakfast. They took their seats at 1045 BST to begin what one minister described as "lively discussions".

Before they began, they assembled for a team photo. Canadian Prime Minister Stephen Harper missed it when he was pulled aside by an aide. When the photo was re-taken, however, the Italian Prime Minister, Silvio Berlusconi, was absent.

Different drafts of the final communique are circulating at the summit, reflecting differing proposals on a number of issues.

The leaders of the world's largest economies are expected to announce measures in the following key areas:

• IMF boost: $500bn of additional money will be loaned to the International Monetary Fund, the emergency lender for countries in financial trouble, in addition to the $250bn already pledged. Its resources have been depleted in recent months by having to help a number of Eastern European nations

• Tax havens: Treasury minister Stephen Timms says the G20 have agreed to impose sanctions on tax havens that refuse to sign up to OECD rules to fight money laundering and tax evasion, although discussions are continuing over whether unco-operative havens will be named and shamed

• Global trade: There will be about $250bn committed to boost international trade, UK Chancellor Alistair Darling confirmed. The figure will include national efforts already announced

• Fiscal stimulus: No new money will be pledged. However, leaders are expected to pledge to do whatever it takes to boost their own economies and emphasise that - globally - $2 trillion is already being spent to tackle the global recession

• Protectionism: There will be a commitment to naming and shaming countries that breach free trade rules

• Financial regulation: Tighter limits on the financial system are expected, including the activities of hedge funds, which are currently unregulated investment funds

• Bankers: There may also be measures to clamp down on bankers' pay.

Senior EU officials, however, have told the BBC's Joe Lynam that there is concern that there will not be as much emphasis on bankers' pay and bonuses as they had hoped.

An agreement in general terms stating that there should be no reward for failure is expected, but fixed terms and conditions may be much harder to agree, EU officials have told our correspondent.