diplomatic gathering, striking a statesmanlike pose at the nearby New York event of ex-president Bill Clinton's humanitarian organisation.
A week before they clash in their first Presidential debate, and as the clock ticks down to the November 6 election with Obama enjoying a clear opinion poll edge, the rivals jousted for foreign policy advantage.
But the interlude was brief for both as Obama skipped back to Washington, with a flurry of trips planned to battleground states and Romney flew off to court undecided voters in the potentially crucial state of Ohio.
The President got an earful from critics for taping an appearance on ABC talk show "The View" -- reaching millions of women voters -- instead of seeing leaders such as Israel's Benjamin Netanyahu and Egypt's Mohamed Morsi.
Obama, painted by Republicans as an apologist for America and an appeaser of US enemies including Iran, was under pressure over his approach to the turmoil spawned by revolutions in the Arab world following recent anti-US attacks.
US President Barack Obama point to people on the South Lawn of the White House in Washington. AP Photo/Carolyn Kaster
In his speech at the UN, the President eulogised ambassador to Libya Chris Stevens, slain two weeks ago, as the epitome of US and UN values, linked Arab Spring aspirations to founding American principles and highlighted progress amid tumult in the Middle East.
Obama stressed that the violence of recent weeks sparked by a YouTube trailer for an anti-Muslim film made on US soil did not "represent the views of the overwhelming majority of Muslims."
Quoting his hero Abraham Lincoln, Obama said he was convinced that "ultimately government 'of the people, by the people and for the people' is more likely to yield stability, prosperity and peace."
US President Barack Obama addresses the 67th United Nations general assembly at the UN headquarters in New York. Reuters/Mike Segar
With an eye on critics led by Romney, who on Monday said Washington should "shape" events in the Middle East, Obama insisted America "has not, and will not, seek to dictate the outcome of democratic transitions abroad."
The President however highlighted US action in Libya, support for a political transition in Yemen and backing for uprisings in Egypt and Tunisia.
He also delivered unequivocal backing for the bedrock US value of free speech, even when it offends other cultures, after critics said he went soft on US core freedoms after the eruption in the Muslim world.
He again condemned the "crude and disgusting video" deemed offensive to Islam and made in the United States which sparked outrage in the Muslim world but insisted it was no excuse for violence.
"We understand why people take offense to this video because millions of our citizens are among them," Obama said, but noted he neither could nor should ban it because of free speech protections enshrined in the US Constitution.
"Moreover, as president of our country, and commander-in-chief of our military, I accept that people are going to call me awful things every day, and I will always defend their right to do so," he said.
Obama also said that in 2012, when "anyone with a cell phone can spread offensive views around the world with the click of a button, the notion that we can control the flow of information is obsolete."
The President also warned Iran that if diplomacy does not change its behavior, the United States would do "what we must" to prevent Tehran getting a nuclear bomb.
While Obama is favored over Romney by voters in most opinion polls on foreign policy, Republicans have been portraying the White House incumbent as weak on Iran and accuse him of ignoring Israeli fears for its security.
Republican Presidential candidate Mitt Romney walks to his campaign plane in Denver, Colorado. Reuters/Brian Snyder
Romney did not allow Obama to have the spotlight to himself, speaking to the Clinton Global Initiative and laying out a plan to link US foreign aid to trade and private enterprise in the developing world.
The Republican then flew to Ohio, the crucial swing state where he trails Obama and which he needs if he is to have a viable path to the White House.
Campaigning in Vandalia, he accused Obama of trying to paper over deadly crises in the Middle East by calling them "bumps in the road," and of failing to stand up to Iran.
"Those developments include 20,000 people being killed in Syria, a Muslim Brotherhood president of Egypt, Iran on the cusp of becoming a nuclear power, and, of course, the assassination of our ambassador in Libya," Romney told CNN.
"I'm not sure whether any of those qualifies as a bump in the road. They certainly don't in my view," he added.Clash of civilizations between Islamic world, West?
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