President Barack Obama and Iranian President Mahmoud Ahmadinejad are set to take their political rivalry to the U.N. General Assembly Thursday amid efforts to renew negotiations over Iran's suspect nuclear program.

Ahmadinejad, who regularly challenges American presidents to debate him in front of the world's media, has a history of using the annual summit to make provocative statements.

In 2008, the Iranian leader called Israel a "Zionist regime" of murderers, igniting outrage. Last year, his comments were so outrageous they prompted a walkout by other nations.

Obama was scheduled to speak Thursday morning and Ahmadinejad in the afternoon. Others scheduled to address the general assembly included leaders from China, Turkey and Iraq.

In his speech to foreign leaders, Obama plans to emphasize efforts his administration is making to promote peace and stability from Iraq and Afghanistan to the Middle East while countering nuclear concerns in Iran and North Korea.

On Wednesday night, a combative Ahmadinejad took to the airwaves to lash out at Israel's prime minister, telling CNN's Larry King that Benjamin Netanyahu is a "skilled killer" who "should be put on trial for killing women and children."

Ahmadinejad deflected questions about his country's nuclear program, saying "we have no interest" in atomic weapons. "We are not seeking the bomb."

On the sidelines of the summit, European Union foreign policy chief Catherine Ashton, Secretary of State Hillary Rodham Clinton and the foreign ministers of Britain, China, France, Germany and Russia met Wednesday to try to find a solution to the long-running dispute over Iran's nuclear ambitions. They urged Iran to come to the table for a new round of talks, and said it remained essential for Iran to prove its nuclear program is peaceful.

The U.S. and key Western allies fear Iran could try to process its low enriched uranium into highly enriched uranium, which could be used to make an atomic weapon. Iran insists its nuclear program is purely peaceful, aimed solely at producing nuclear energy.

Iran has defied four rounds of increasingly restrictive economic sanctions aimed at compelling Tehran to prove it is not building a nuclear weapons program. Iran adamantly denies accusations from the U.S. and its allies that it seeks atomic arms.

Talks with Tehran reached a stalemate last October, after Iranian officials tried to renegotiate an agreement to ship most of its low enriched uranium out of the country, to be turned into fuel for a research reactor.

In their meeting on Wednesday, Clinton and the other ministers said they still want to engage with Iran on a fuel swap for its research reactor. They backed the readiness of U.N. nuclear agency chief, Yukio Amano, to convene a meeting.

"We look forward to Iran's positive and constructive participation in this dialogue," they said.

The meeting comes on the heels of a three-day summit to promote the achievement of U.N. anti-poverty goals by the 2015 target that wrapped up late Wednesday night. Presidents, prime ministers and kings from many of the U.N.'s 192 member states who attended the summit are remaining in New York and will shift gears to other world issues from the continuing impact of the global financial crisis to terrorism and nuclear proliferation at the ministerial meeting.

On the summit's last day, nations pledged more than $40 billion to battle needless deaths among poor mothers and their children. But the struggling world economy, particularly in the United States, raises deep concerns that the cash won't be forthcoming. Leaders exhorted financial donors to fulfill their aid commitments.

"The crisis is no excuse for letting up our efforts, but underscores the need for actions," U.N. Secretary-General Ban Ki-moon said as he wrapped up the three-day Millennium Development Goals summit.

With many countries still hurting from the global economic crisis, the secretary-general has repeatedly urged governments not to abandon the world's 1 billion people living on less than $1.25 a day. The United States and Britain said they will continue to do their part to help the global poor.

"We will keep our promises and honor our commitments," Obama told world leaders.

"I suspect that wealthier countries may ask -- with our economies struggling, so many people out of work, and so many families barely getting by, why a summit on development?" he said. "The answer is simple. In our global economy, progress in even the poorest countries can advance the prosperity and security of people far beyond their borders, including my fellow Americans."

Britain's Deputy Prime Minister Nick Clegg urged other countries to join Britain in meeting aid commitments.

The goals, "are not simply charity, nor are they pure altruism," Clegg said. "They are also the key to lasting safety and future prosperity."

International aid group Oxfam called the summit "a mirage."

"The promises look good from a distance, but the details are hard to see, and when the world's poorest people most need help, pledges could still vanish into thin air," Oxfam spokeswoman Emma Seery said in a statement.

"While leaders celebrated a big package of money for global health, they failed to acknowledge their collective disastrous failure to meet their aid targets, which is putting the lives of women and children at risk daily," she said.

The issues of maternal and child mortality have been a particular focus of the summit, which reviewed efforts to implement anti-poverty goals adopted in 2000 -- and found them lacking. Worldwide every year, an estimated 8 million children still die before reaching their 5th birthday, and about 350,000 women die during pregnancy or childbirth.

Along with easing maternal and child mortality, the goals included cutting extreme poverty by half, ensuring universal primary education and halting and reversing the HIV/AIDS pandemic.

The leaders approved a final document saying the U.N. goals can be achieved and spelling out specific actions to accelerate their implementation over the next five years.

One of the last speakers Wednesday night was Melinda French Gates, co-founder of the Bill and Melinda Gates Foundation, who said she's impatient but optimistic because of the progress she's seen in the last 10 years to meet the goals.

"I'm optimistic that our sense of urgency will inspire us to work together, not to isolate ourselves, for if we are motivated, if we are inspired, if we work together, then we can meet again in five years to celebrate achievements that few of us might have dared to imagine," Gates said.

The Associated Press contributed to this report.