(AP) - President Barack Obama challenged worldleaders Wednesday to shoulder more of the globe's critical burdens,promising a newly cooperative partner in America but sternlywarning they can no longer castigate the U.S. as a go-it-alonebully while still demanding it cure all ills.

"Those who used to chastise America for acting alone in theworld cannot now stand by and wait for America to solve the world'sproblems alone," said Obama in put-up-or-shut-up comments before apacked U.N. General Assembly hall. "Now is the time for all of usto take our share of responsibility for a global response to globalchallenges."

In his first appearance before the group, Obama promised theU.S. would reach out in "a new era of engagement based on mutualinterest and mutual respect," but he also wagged a rhetoricalfinger at leaders who spend much of their time at internationalgatherings excoriating the U.S. He said "an almost reflexiveanti-Americanism" that swept the globe under the administration ofhis predecessor, George W. Bush, is not "an excuse for collectiveinaction."

"Nothing is easier than blaming others for our troubles andabsolving ourselves of responsibility for our choices and ouractions," he said.

And yet, directly following Obama at the podium was Libyanleader Moammar Gadhafi, who railed against the U.N. SecurityCouncil, which includes the U.S., calling it a "terror council"and accusing it of treating smaller nations as "second class,despised."

U.S. presidents - Bush included - have come to the UnitedNations year after year with a wish list of action items andpreaching the gospel of working together. The U.S. is rich andpowerful, but cannot solve problems without help from the rest ofthe world, they say, whether Democrat or Republican.

So Obama's message at its core was not new.

But it was delivered in an unmistakably new, more humble tone.

Following a president criticized for makingmy-way-or-the-highway "requests" of allies, Obama didn't demandso much as he chided and cajoled. It's now an inextricablyinterconnected world, he said, so that each country's problemsbecome the others' and hardly anything can be solved in one placewithout participation from elsewhere.

"In the year 2009 - more than at any point in human history -the interests of nations and peoples are shared," Obama said.

And he delivered the message that America will not behave as ifit is better than anyone else.

Even while offering what he called "a new chapter ofinternational cooperation" from Washington, Obama was blunt thatothers must step up or face dire consequences: "extremists sowingterror in pockets of the world, protracted conflicts that grind onand on, genocide, mass atrocities, more nations with nuclearweapons, melting ice caps and ravaged populations, persistentpoverty and pandemic disease."