By Jorn Madslien
BBC News business reporter at the G7 meeting in London
Chancellor Gordon Brown has called for the removal of barriers to global trade to promote stability and growth.
Mr Brown is expected to push for more aid to Africa
Ahead of the meeting of G7 finance ministers and central bankers in London, he called on them to "rise to the global challenge".
"We have to build a shared economic purpose," he said, warning that nations' prosperity would depend on their ability to face tough decisions.
The London meeting kicks off the UK's presidency of the G7 rich nations club.
"Within 20 years half the world's manufactured exports could come from developing countries and within a decade five million US and European jobs could be outsourced," Mr Brown said.
In addition to the G7 mandate, the UK will also hold the European Union (EU) presidency for six months this year.
Mr Brown said the UK would use the EU Presidency "to push forward a new transatlantic trade and investment partnership to remove regulatory and other barriers between the European Union and the USA".
Mr Greenspan will give a keynote speech on Friday
Following the opening speech, Mr Brown and other G7 finance ministers retreated to a closed-door meeting to discuss the world economy.
US Federal Reserve chairman Alan Greenspan, who is to make a keynote speech later on Friday, and other central bank governors, as well as finance ministers from China, India, Brazil, South Africa and Russia are also taking part.
Ahead of the meeting, Mr Brown said that he would urge the finance ministers to take action to ensure enduring global prosperity, saying "We will look at how each continent can contribute to that".
The finance ministers are expected to put pressure on China to relax its pegged currency regime, though few expect the country to be swayed.
The governor of China's central bank gave away no clues on future exchange rate at a press conference on Friday, which he used to reiterate China's willingness to work with international bodies like the G7 to "keep the global economy more balanced".
Separately, Mr Brown is expected to push for extra aid and debt relief for Africa, and again there is slim hope that a firm agreement will be reached during the two-day summit.
Among the G7 finance ministers, the Europeans tend to agree with Mr Brown's arguments while Japan and the US are expected to be harder to convince.
An anti-poverty rally was held in London's Trafalgar Square on Thursday to put pressure on the finance ministers.
Among those addressing the crowd was the former South African President Nelson Mandela.
Parallel discussions - organised by the UK Treasury - on advancing enterprise are also taking place.
This will involve discussion sessions attended by chief executives from some of the world's largest companies, including GE chief Jeff Immelt, BP chief Lord Browne and AstraZeneca chief Sir Tom McKillop.
Mr Brown also ventured beyond the international focus of the day by outlining his vision for Britain's economic future, saying he wanted it to "be not only the most stable environment, but the most attractive location to do business and to create new business".
On Friday night, the finance ministers and central bank governors will attend a working dinner. The meeting concludes on Saturday.