UNITED NATIONS: US President Barack Obama Wednesday delivered a stern message to global leaders to work together to solve the world’s most pressing problems in his maiden speech to UN General Assembly.

“Those who used to chastise America for acting alone in the world cannot now stand by and wait for America to solve the world’s problems alone,” Obama said after receiving warm applause from some 120 heads of state and government.

“Because the time has come for the world to move in a new direction,” he said. “We must embrace a new era of engagement based on mutual interest and mutual respect and our work must begin now.”

With Presidents Muammar Qaddafi of Libya and Mahmoud Ahmadinejad of Iran also due to speak, Obama addressed the UN General Assembly for the first time since he moved into the White House in January.

UN chief Ban Ki-moon opened the debate and set the tone calling for “genuine” collective action to roll back climate change as well as global poverty and push for nuclear disarmament.

“If ever there were a time to act in a spirit of renewed multilateralism — a moment to create a United Nations of genuine collective action — it is now,” Ban told the assembly.

But all eyes were on Obama who has vowed a close partnership with the United Nations after the administration of his predecessor, George W. Bush, was accused of riding roughshod over the 192-member body.

And the US leader had some sharp words for the United Nations, saying “sadly, but not surprisingly, this body has often become a forum for sowing discord instead of forging common ground.

“After all, it is easy to walk up to this podium and to point fingers and stoke division. Nothing is easier than blaming others for our troubles, and absolving ourselves of responsibility for our choices and our actions.”

The annual political pow-wow was fraught with the potential for unwanted public encounters between foes. But Obama avoided Qaddafi, who delayed proceedings by not appearing immediately at the podium, for his first ever speech to the UN in his four decades in power.

In a reminder of the dangers facing the world, in the city still scarred by the Sept. 11, 2001 attacks on the World Trade Center, Obama warned of the heavy price to pay if global leaders fail to act against militants.

“Consider the course that we are on if we fail to confront the status quo. Extremists sowing terror in pockets of the world. Protracted conflicts that grind on and on,” the president said. “Genocide and mass atrocities. More and more nations with nuclear weapons. Melting ice caps and ravaged populations. Persistent poverty and pandemic disease,” he added.

And ahead of a UN Security Council meeting on nuclear disarmament he will chair Thursday, Obama warned “the threat of proliferation is growing in scope and complexity. “If we fail to act, we will invite nuclear arms races in every region, and the prospect of wars and acts of terror on a scale that we can hardly imagine.”

President Luiz Inacio Lula da Silva of Brazil, who has pledged to champion the cause of emerging democracies, China’s Hu Jintao and Russian President Dmitry Medvedev were also take to the floor on Wednesday.