U.S. President Barack Obama denied rifts between the world's leading economies on the eve of a crisis summit and urged them on Wednesday to act together to find the fastest route out of global recession.

Effective action by the Group of 20 would make the difference between an early recovery and a 'slow rolling crisis', the U.S. president declared on his first major foreign trip since taking office.

I know that G20 nations are appropriately pursuing their own approaches...We're not going to agree on every point, he told reporters in London.

I came here to put forward ideas but I also came here to listen, not to lecture. Having said that, we must not miss an opportunity to lead, to confront a crisis that knows no borders.

Obama, on his first appearance on the international stage, is under pressure to show that the country where the global crisis began can lead the way out.

I am absolutely confident that this meeting will reflect enormous consensus about the need to work in concert to deal with these problems, he told a joint news conference with British Prime Minister Gordon Brown.

Obama said the duration of the crisis would depend on how effectively countries tackled a series of challenges in the coming months: financial regulation, helping banks deal with toxic assets, managing capital outflows from emerging markets, shielding the poorest countries and reforming international financial institutions.

All those things will help determine whether this ends up being a slow rolling crisis, that takes a lot more time to cure it, or whether we start seeing significant recovery, he said.

I don't think there is any doubt that 2009 is going to be difficult.

FRENCH INTERVENTION

Obama spoke hours after French President Nicolas Sarkozy said neither France nor Germany was satisfied with proposals currently on the table and declared that he would reject false compromises at the summit.

Washington, which is pushing through an economic stimulus package worth $787 billion or about 5.5 percent of Gross Domestic Product for 2009-10, is pushing hard for other governments to pump in more money too.

But France and Germany say they do not want this to distract from the need to regulate and rein in financial market excess.

Obama said differences between the various countries had been vastly overstated.

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, he said.

The idea that some parties were pushing for greater financial regulation and others resisting such a move was also belied by the facts, he said. And there was complete concurrence that emerging economies needed more resources to help them weather the storm.

There's a great desire to inject some conflict and some drama into the occasion, but the truth of the matter is I think there's been an extraordinary convergence and I'm extremely confident the United States, as a peer of these other countries, will help to lead us through this very difficult time.

Obama said all parties had a responsibility to act with urgency and to reject protectionism.

People are losing their homes, losing their businesses...People around the world who were already desperate before the crisis may find themselves even more desperate afterwards, he said.

Make no mistake, we are facing the most severe economic crisis since World War Two.

(Writing by Mark Trevelyan; editing by Janet McBride)

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