US President Barack Obama will lead Western demands for action on the Syrian civil war at the start of the UN General Assembly on Tuesday, AFP reports.
Obama will be one of the opening speakers at the annual meeting of world leaders where the 18-month-old Syria conflict, mounting fears of a military strike on Iran and anti-West protests in Muslim nations are set to dominate.
UN leader Ban Ki-moon, France's President Francois Hollande and Qatar's emir, Sheikh Hamad bin Khalifa Al-Thani, a key backer of the Syrian opposition, are also expected to lambast President Bashar al-Assad on the opening morning.
The diplomatic assault will go on all week as Arab and European leaders vent the outrage which has increased since UN-Arab League envoy Lakhdar Brahimi warned Monday that the conflict is worsening with no immediate hope of ending the war.
Brahimi accused Assad of using "medieval" style torture on opponents.
The Islamist occupation of northern Mali, conflict in eastern Democratic Republic of Congo and Somalia's attempts to build a new state out of the ruins of war will also be raised by leaders in New York.
The debate will probably be Obama's last major foreign policy speech before the US election on November 6. There will be none of the normal meetings with world leaders. Obama will spend only a day in New York before heading back to the campaign trail against Mitt Romney.
Still, the White House insists the speech will go further than domestic politics. "This is not a campaign speech," said White House spokesman Jay Carney.
"This is a speech in which the President will make clear his views, the administration's positions and America's role with regards to a lot of transformation that's happening in the world."
Stung by the anti-Islam video which sparked deadly anti-US protests in Muslim nations, Carney said Obama would reiterate that the United States will "never retreat from the world" and will deliver justice to those who harm Americans.
Obama is also likely to warn Iran that time is running out for a diplomatic exit from the showdown over its nuclear drive and renew his vow that he will use force, if necessary, to stop an Iranian atomic weapon.
Iran's President Mahmoud Ahmadinejad defiantly warned Monday that his country did not fear a possible Israeli strike on its nuclear installations.
Obama's fleeting visit to the United Nations will not include talks with Israeli Prime Minister Benjamin Netanyahu, with whom he has publicly differed over the Iranian nuclear crisis.
Aides said Obama's compressed election schedule did not allow time for a meeting, sparking Republican criticism, intensified by Obama's comment in an interview Sunday that Israeli warnings over Iran were "noise."
While the UN assembly is traditionally a forum for a US president to address the world, Obama's speech this year will still have a domestic undercurrent because of Romney's election attacks on his foreign policy.
Obama and his rival will also separately address the Clinton Global Initiative, the annual meeting of former president Bill Clinton's humanitarian foundation.
Romney on Monday accused Obama -- who Sunday spoke of "bumps in the road" following Arab Spring revolutions -- of minimizing the murder of four Americans including US ambassador to Libya Christopher Stevens in Benghazi.
"When the president was speaking about bumps in the road he was talking about the developments in the Middle East and that includes an assassination," Romney told NBC News.
"It includes a Muslim Brotherhood individual becoming president of Egypt, it includes Syria being in tumult, it includes Iran being on the cusp of having nuclear capability, it includes Pakistan being in commotion."
Polls show Obama is favored over Romney to handle foreign policy, but the Democratic narrative has been complicated by events at the US consulate in Benghazi and wider anti-American fury rocking many Muslim nations.