United Nations Secretary General Kofi Annan has told leaders at a summit of developing nations that the world must solve the problems of the Middle East.
A frail looking Fidel Castro greeted Kofi Annan in hospital
Mr Annan told the Non-Aligned Movement in Cuba that the war in Lebanon had been a wake up call to the world.
He also urged leaders to respect human rights, to end oppression and to honour press freedom.
The summit was opened by Cuba's acting leader Raul Castro, in the absence of his sick brother, Fidel.
The long-time communist leader is still recovering in hospital from intestinal surgery he underwent more than a month ago.
Mr Annan visited the Cuban president in hospital before delivering his speech.
The UN chief said the Lebanon crisis had made nations "more and more convinced of the need to deal with the root causes of the problem" in the Middle East.
"The daily violence we are witnessing in Iraq and Afghanistan provides a powerful reminder that, without judicious intervention on the political front, the slide to anarchy and civil war becomes inexorable."
But he also stressed that leaders should look after the welfare of their own people. "We need governments of the south to fulfil their obligations to their people at home," Mr Annan said.
Raul Castro has been taking on his brother's duties
The leaders of more than 50 developing countries have gathered in Cuba for the summit, which brings together 118 nations - nearly two-thirds of the UN's members - including many developing countries, for an alternative forum of debate.
The BBC's Stephen Gibbs, in Havana, says the huge cast list of dignitaries at the two-day summit includes some of Washington's least favourite world leaders.
They include Hugo Chavez of Venezuela, Mahmoud Ahmadinejad of Iran, Zimbabwe's Robert Mugabe and Belarus' Alexander Lukashenko.
And while Fidel Castro was not present to deliver his usual fiery anti-American rhetoric, brother Raul continued in the same vein.
He accused the US of trying to effect regime change in Cuba and destroy its social system, and condemned US actions elsewhere.
"The risk of aggression and more wars of imperial conquest is more serious and more widespread than ever," he said.