LONDON  Struggling to bridge deep divides over how to revive a paralyzed global economy, the leaders of the world’s largest economies agreed Thursday to bail out developing countries, stimulate world trade and regulate financial firms more stringently. But President Obama conceded that there were “no guarantees” that those measures would reverse the biggest global downturn in six decades.

Prime Minister Gordon Brown of Britain, host of the Group of 20 summit meeting called to fight the crisis, announced at its conclusion that the leaders had committed to $1.1 trillion in new funds that would greatly increase the capital available to the International Monetary Fund. The goal would be a revival in trade, which is expected to contract this year for the first time in 30 years.

But the combination of loans and guarantees fell short of an injection of fresh fiscal stimuli into the economic bloodstream  the result of a stubborn division between Continental Europe and the United States over whether to act now or wait to see whether existing spending measures took effect.

Moreover, the final accord was far more forceful in addressing the plight of emerging economies that had been sideswiped by the financial crisis than it was in addressing the deep recession in the largest countries where the crisis began.