* OECD says world shrinking faster than expected
* World Bank announces $50 billion trade programme
* Japanese PM says plans new stimulus package
* Markets seen performing best in March in six years (For more on the global financial crisis, click)
By Lesley Wroughton and Anna Willard
LONDON/PARIS, March 31 (Reuters) - World leaders travelling to London for this week's G20 crisis summit got a stark reminder on Tuesday about the size of the economic storm they face.
The Organisation for Economic Co-Operation and Development (OECD) forecast the world economy would shrink far faster than originally expected, sending unemployment soaring and underscoring the need for extra steps to halt the crisis.
World Bank President Robert Zoellick responded by announcing a $50 billion programme to counter the decline in world trade.
Speaking at the London offices of Thomson Reuters, Zoellick also backed the dollar as the world's main reserve currency but said he feared the world economy could stumble further into recession. The 30-nation OECD, releasing its outlook as Japan announced it was readying a third economic stimulus package, said member economies would shrink 4.3 percent this year. That compares with a forecast of a 0.4 percent contraction made in November
"The world economy is in the midst of its deepest and most synchronised recession in our lifetime caused by a global financial crisis and deepened by a collapse in world trade," the Paris-based OECD said.
"We anticipate that the ongoing contraction in economic activity will worsen this year before a policy-induced recovery gradually builds momentum through 2010." Both Japan and Germany announced big rises in unemployment, underscoring the human cost of the crisis that leaders of the world's richest nations and biggest emerging economies must tackle when they meet in London on Thursday.
U.S. President Barack Obama was due to arrive for the talks in London on Tuesday evening, carrying a hefty agenda of how he sees the world dealing the crisis.
This will be the first major overseas trip of Obama's presidency, during which he will hold bilateral talks with the leaders of China and Russia among others before going on to a NATO summit and visiting the Czech Republic and Turkey.
JAPANESE STIMULUS
In Japan, Prime Minister Taro Aso, pledged to submit an extra budget to fund a new stimulus package to fight recession at home but was silent on how much the government would spend.
Aso, who has been faring badly in opinion polls, told reporters in Tokyo: "We aim to compile bold measures without being fixated on past experiences."
The planned package, which would be the third since the economic downturn, will likely aim to create 2 million jobs over three years.
Japanese unemployment hit a seasonally-adjusted 4.4 percent in February from 4.1 percent in January, while household spending slid 3.5 percent in February from a year earlier.
Germany reported its biggest jump in unemployment in March since the economic crisis began, figures from the Federal Labour Office showed.
"The German labour market is increasingly feeling the pain of the country's worst recession in decades," economist Carsten Brzeski of ING Financial Market said after adjusted numbers for March took German unemployment to 8.1 percent.
Inflation for the 16 European countries in the euro zone, was down to a record low of 0.6 percent year-on-year in March, bolstering expectations of an ECB rate cut on Thursday.
Markets expect the European Central bank (ECB) to reduce rates by half a percentage point to 1.0 percent and perhaps announce measures to boost liquidity.
While indicators pointed to a worsening global economy, stock markets looked set to achieve their best monthly performance in more than six years this month.
That was relative, however, with the MSCI World index still down more than 12 percent this quarter after losing 22.7 percent in the October-December period last year.
BROWN CALLS FOR COMMITMENT
British Prime Minister Gordon Brown, the host of the G20 summit, said leaders would only succeed in tackling the economic and financial crisis if all nations committed to act together.
Brown 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.
With big demonstrations planned against the G20 meeting in London and fears some could end in violence, Brown said in a television interview he understood public anger at the global recession but warned it should not be allowed to boil over. (Additional reporting by Yuzo Saeki in TOKYO, Stella Dawson and Dominic Lau in LONDON; Writing by Malcolm Davidson; Editing by Keiron Henderson)