By Emilio San Pedro
BBC Americas editor
Summit leaders have pledged to co-operate to restore economic growth
Brazilian President Luiz Inacio Lula da Silva has hailed the G20 summit as a historic meeting, representing a seismic shift in global politics.
President Lula said he would never have been able to imagine emerging powers like Brazil would be given such a role in restructuring the global economy.
He also said the G8 was no longer relevant in today's globalised world.
At the summit, the G20 agreed a plan to stimulate economic growth with interest rate cuts and government spending.
It also asked finance ministers to produce ideas for reforming the way banks and other financial institutions are regulated.
These ideas will be discussed at a follow-up summit next April.
Global economic reality
President Lula was in rare no-holds barred form at the G20 summit in Washington.
He told reporters that the Group of Eight (G8) - the world's seven leading industrialised nations plus Russia - was an organisation that was no longer viable, calling it irrelevant.
"There is no logic to making any political and economic decisions without the G20 members - developing countries must be part of the solution to the global financial crisis," he said.
And, it could be argued that President Lula had good reason to be so blunt.
After all, as he pointed out, it is the world's richest countries that have been at the centre of the current global economic crisis.
He said it was now up to them to solve their economic problems before they made things even worse for the developing world.
Emerging economic powers sense that the time has come to stake their claim
After the summit, he hailed as historic the decision agreed at the meeting to give a role to the emerging economic powers like Brazil, China and India in restructure the global economy.
He said it was something that he would have never dreamed could have been possible even six months ago.
And, his comments were echoed by Indian Prime Minister Manmohan Singh, who said the crisis served as proof that countries which were excluded in the past must be included in the future.
Mr Singh added that whatever economic model was chosen to deal with the current international crisis, it would have to be genuinely multilateral and reflect the changes in the global economic reality.
It is clear that the emerging economic powers, which have for years been demanding a greater say in international affairs, sense that the time has come to stake their claim.