UN chief Ban Ki-moon on Tuesday stressed the need for "global leadership" as he pressed world leaders not to pursue narrow national interests in the face of hard economic times.
"I see a danger of nations looking more inward, rather than toward a shared future," he said at the opening of the UN General Assembly's annual debate.
He spoke of a "challenge of global leadership" to tackle the world's worsening financial, energy and food crises.
"We see new centers of power and leadership -- in Asia, Latin America and across the newly developed world," Ban told more than 120 heads of state or government, including Presidents George W. Bush of the United States and Nicolas Sarkozy of France.
"In this new world, our challenges are increasingly those of collaboration rather than confrontation," he added.
"Nations can no longer protect their interests, or advance the well-being of their people, without the partnership of the rest."
On the world's current financial crisis, the UN secretary general stressed the need to "restore order to the international financial markets".
"We need a new understanding on business ethics and governance, with more compassion and less uncritical faith in the 'magic' of markets," the UN boss said.
Ban, who has chosen implementation of key poverty reduction goals as a major theme of this year's debate, said he saw "a danger of retreating from the progress we have made, particularly in the realm of development and more equitably sharing the fruits of global growth."
"Global growth has raised billions of people out of poverty. However, if you are among the world's poor, you have never felt poverty so sharply."
On Thursday, he will host a summit meeting on implementation of the poverty reduction Millennium Development Goals (MDGs) on the margins of the General Assembly session.
Ban said he would use Thursday's summit to press world leaders, the private sector, foundations, and civil society to make "ambitious and concrete" proposals to ensure that these goals are implemented by a 2015 deadline.
Monday, a summit meeting on Africa's development needs adopted a political declaration urging rich countries to honor their pledge to double their annual aid to the continent, which is struggling to meet the MDGs.
And returning to the theme of global leadership, Ban told the assembly: "It takes leadership to honor our pledges and our promises in the face of fiscal constraints and political opposition.
"It takes leadership to commit our soldiers to a cause of peace in faraway places. It takes leadership to speak out for justice. To act on climate change despite wonderful voices against you."