US President Barack Obama said on Wednesday there was "enormous consensus" between the world's largest developed and emerging economies on plans to haul the world out of the deepest downturn since the 1930s.

Obama played down any differences with France and Germany, which insisted again on the eve of the summit that G20 countries must agree on measures to tighten financial regulation and crack down on tax havens rather than simply make promises.

Protesters smashed windows and clashed with police in London's financial district. Up to 400 demonstrators attacked offices of the Royal Bank of Scotland, shouting "These streets, our streets! These banks, our banks!"

The Royal Bank of Scotland has become a lightning rod for anger over banker excess that is blamed for the financial crisis. Rescued by the British government last October, RBS continues to pay its former boss an annual pension of around 700,000 pounds ($1 million).

Obama, making his first official visit to Europe, said G20 nations were not going to agree on every point but pushed aside suggestions the summit would falter because countries were split over the importance of regulation versus new stimulus packages.

"The core notion that government has to take some steps to deal with a contracting global market place and that we should be promoting growth -- that's not in dispute," Obama said at a news conference with British Prime Minister Gordon Brown.

"On the regulatory side, this notion that somehow there are those who are pushing for regulation and those who are resisting regulation is belied by the facts."

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