The Prime Minister said the deal was "not the end of poverty in Africa but it is hope that it can be ended".
He said also that the G8 leaders had agreed a further 3 billion dollar package of assistance for the Palestinian Authority.
Mr Blair said the G8 leaders had refused to be deflected by the London bombings and their agreements offered hope in the face of the terrorist outrages.
"We speak today in the shadow of terrorism but it will not obscure what we came here to achieve," he said.
"The purpose of terrorism is not only to kill and maim the innocent, it is to put despair and anger and hatred in people's hearts.
"It is, by its savagery, designed to put all conventional politics in darkness."
Mr Blair acknowledged that the deal on Africa was not all that campaigners had been hoping for but insisted that it represented real progress.
"It isn't the end of poverty in Africa but it is the hope that it can be ended. It isn't all that everyone wanted but it is progress, real and achievable progress," he said.
"It is the definitive expression of our collective will to act in the face of death and disease and conflict that is preventable."
On climate change, Mr Blair said that a process had been agreed with a plan of action to open a dialogue with the emerging economies to "slow down and then in time reverse" the rise in greenhouse gas emissions.
He said this would begin with an international meeting in Britain on November 1.
Mr Blair said that the Africa plan included a 50 billion dollar "uplift" in aid, the "signal" for a new deal on trade and the cancellation of the debts of the poorest nations.
It also involved universal access to Aids treatment, a commitment to a new peacekeeping force for Africa and a commitment by African leaders to democracy and good governance.
"All of this does not change the world tomorrow. It is a beginning, not an end. And none of it today will match the same ghastly impact of terror," he said.
"But it has a pride and a hope and humanity at its heart that can lift the shadow of terrorism and light the way to a better future."Reuse content