"We believe that the world is more secure and the interests of the United States are best advanced, when we act collectively," Obama said at the inauguration of the Ronald H Brown United States Mission to the UN building here.
"The burden of action should not always be America's alone," he told the audience. "So in Libya today we see a broad and growing coalition, including Arab partners."
On Feb 26, the UN Security Council slapped sanctions on the Libyan regime including an arms embargo, an asset freeze and travel ban on Gaddafi and his loyalists, and a referral to the Hague-based International Criminal Court.
In March, the Security Council called for an immediate ceasefire, establishing a no-fly zone and authorised "all necessary measures" for protecting civilians in Libya.
India, China, Russia, Brazil and Germany had abstained from voting on the resolution.
Obama made a strong case for intervention to protect human rights and stop atrocities when other options had failed in the North African country.
"We believe that force should not be the first option," Obama said. "We understand the costs and risks involved in the use of force."
"What we''ve learned from bitter experience -- from the wars that were not prevented, the innocent lives that were not saved -- is that all that's necessary for evil to triumph is that good people and responsible nations stand by and do nothing," he added.
UN Secretary-General Ban Ki-moon as well as representatives from more than 30 countries, including US Secretary of State Hillary Clinton yesterday attended a conference on Libya in London.
"When the air strikes began, government forces were poised to enter Benghazi," Ban said in London. "A bloodbath appeared to be inevitable."
"For now, we have prevented a humanitarian catastrophe. Yet we also know: air operations, alone, will not resolve the crisis," the UN Secretary-General said.
In London, leaders agreed that Muammar Gaddafi must go but what will happen to him remains uncertain. There has reportedly already been some talk of letting him leave the country.
"Stop your barbaric, unjust offensive on Libya. Leave Libya to Libyans," Gaddafi said in a letter to the leaders meeting in London.
Obama said that the current action was making clear that "the United States of America, and the world, stand with those who seek to determine their own destiny, free from fear, and free to dream of a day when they, too, can live in justice and dignity."
Earlier in the day, Obama also stopped at the American Museum of Natural History for interview with the US media and at the New York City Science and Engineering Fair.