The World Bank announced a $50 billion program on Tuesday to counter a decline in global trade and Britain called on G20 leaders to supply the oxygen of confidence to save the world economy from recession.

Leaders of the world's largest and developing economies meet in London on Wednesday and Thursday to try to chart a way out of the worst global crisis since the 1930s, caused by a freeze in credit after bank loans went bad.

The scale of the problem was underlined by the OECD, which said the economies of its 30 members would shrink by 4.3 percent this year, shedding 25 million jobs this year and next.

Japan, the world's no. 2 economy, announced plans for its third stimulus package and Japanese media predicted it would aim to create 60 trillion yen ($612 billion) worth of demand and 2 million jobs.

The OECD's chief economist Klaus Schmidt-Hebbel said international stimulus measures taken so far should restore growth in 2010 -- a forecast that echoed a line in a draft G20 communique obtained by Reuters on Monday.

The draft shows leaders want to agree to avoid currency moves and protectionist measures that would damage other economies. It also repeats existing promises to get economies back on track, but does not contain any specific details

British Prime Minister Gordon Brown, the summit host, said G20 leaders should aim to save or create 20 million jobs and must act together to increase the potential impact of their actions.

Leaders meeting in London must supply the oxygen of confidence to today's global economy and give people in all of our countries renewed hope for the future, he said.

Speaking to Reuters ahead of the summit, World Bank President Robert Zoellick played down the chances of a dethroning of the dollar as the world's leading currency.

I think the dollar will remain the principal reserve currency. The question will be whether you have complementary measures, Zoellick said.

Zoellick also said the Bank expects world trade volumes to fall by 6 percent this year, the largest decline in 80 years.

While he offered few details about the program to boost trade, which is being considered by the World Bank board later on Tuesday, Zoellick said the drop in commerce was exacerbated by a shortfall in trade credit, which allows exporters and importers to settle accounts.

HOST BROWN SEEKS CONFIDENCE

The run-up to the summit has been marked by divisions between the United States and continental Europe over its focus.

President Barack Obama's U.S. administration has been pushing for further fiscal stimulus, whereas countries like France and Germany want to see the impact of measures already taken and focus on reforming regulation of financial markets.

Brown, who has spearheaded efforts to get agreement on concrete measures at the G20, said the summit must restore people's faith in the economy.

The world didn't come together in previous recessions and they lasted much longer, he told Britain's Good Morning Television. The most important thing is that we all act together, because if we act with other countries, it's got twice the effect than if we do it on our own.

The son of a Scottish church minister, Brown told faith leaders and charity workers in a speech in London's St Paul's Cathedral that markets must be guided by everyday values cherished by all.

Our task today is to bring the imperatives served by our financial markets into proper alignment with the values held by families and business people across our country - hard work, taking responsibility, being honest, being fair, Brown said.

Obama is due to arrive in London on Tuesday evening on his first visit to Europe since he became president.

Security in London will be tight, with anarchist groups planning protests on Wednesday at the Bank of England.

Police in southwest England arrested five people suspected of planning to join protests after weapons were found during a raid on a house, police said on Monday.

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