• IMF boost: The resources of the International Monetary Fund, the emergency lender for countries in financial trouble, will be expanded by $750bn. Its coffers have been depleted in recent months by having to help a number of Eastern European nations
The G20 nations are expected to agree to lend it an extra $500bn. In addition, leaders will also agree significant changes that will in effect create an overdraft facility worth $250bn (in the IMF's currency, so-called Special Drawing Rights) that the world's poorest countries can call on
• 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.
According to the BBC's diplomatic correspondent James Robbins, the agreement will mark a very substantial shift towards control and regulation of capitalism.
It does imply that business will be done in a very significantly different way in the future, he says.
Earlier, UK Business Secretary Lord Mandelson told the BBC that despite all the preparatory work before the summit, there were still some issues to iron out.
Geldof: National grandstanding is over
"[Disagreements] persisted overnight," Lord Mandelson told the BBC News channel, particularly over levels of funding for the IMF, regulation of tax havens and measures to boost global trade.
It is understood that Gordon Brown wants to go further than some other leaders on these matters.
"Our Prime Minister is excessively ambitious in what he wants out of this summit," UK Business Secretary Lord Mandelson said. "A good thing too, because there's absolutely no point in people just coming here and rehearsing old arguments restating old commitments."
Leaders started the crucial day of talks with a working breakfast, and before beginning what one minister described as "lively discussions", posed 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.
Protesters gathered outside the summit, but in smaller numbers than Wednesday's demonstrations in London's financial district where one man died and 86 people were arrested.
By mid-afternoon on Thursday, that total had risen to 111, the Metropolitan police said.
Several hundred staged "noisy but calm" protests near the Excel centre representing groups including the Stop the War Coalition and CND, the BBC's Ben Brown said.
A small group of protesters gathered earlier at the London Stock Exchange, but have since dispersed.
The final agreement will not be the end of the process, BBC chief economics correspondent Hugh Pym warns. "The G20 will need to meet again."
He says the leaders will have a difficult balancing act in presenting the final agreements later on Thursday.
There will have to be a bit of pragmatism over what can and cannot be achieved, our correspondent says, but they must also convey a sense that they really have a vision as to how they can bring economies through this recession.
The recession has worsened since G20 leaders met last November in Washington.
Both the IMF and the World Bank expect the world economy to shrink for the first time in decades this year.
Reporting from from the Excel centre, BBC business correspondent John Moylan said the summit would be judged a success if the global recession became a short, sharp shock, rather than a very long downturn.
The G20 group of nations is made up of the world's most powerful economies, accounting for 90% of the world's economic output, 80% of world trade and two-thirds of the world's population.
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