UNITED NATIONS - President Barack Obama pressed world leaders on Wednesday to help confront challenges ranging from the war in Afghanistan to nuclear standoffs with Iran and North Korea instead of expecting the United States to do it all alone.

Reflecting the pressure he faces for results on a slew of foreign policy problems, Obama issued a blunt message in his United Nations debut that other countries must shoulder a larger burden in tackling international crises.

Those who used to chastise America for acting alone in the world cannot now stand by and wait for America to solve the world's problems alone, Obama said. Now is the time for all of us to take our share of responsibility.

Obama used his time in the world spotlight to stress his shift in tone from the go-it-alone cowboy diplomacy of his predecessor George W. Bush, which alienated some friends as well as foes.

But Obama's emphasis on multilateral cooperation, while welcomed by many in the world, has yet to yield much in the way of tangible foreign policy achievements.

During his wide-ranging speech, Obama said he remained committed to diplomacy with Iran and North Korea but that both nations must face consequences if they chose to pursue nuclear weapons.

If the governments of Iran and North Korea ... are oblivious to the dangers of escalating nuclear arms races in both East Asia and the Middle East, then they must be held accountable, he said.

Tehran and Pyongyang are examples of how Obama's vow to engage America's foes has been met mostly with defiance.

But with Iran's much-anticipated talks with the United States and other world powers set for October 1, Obama walked a cautious line, avoiding any specific threat of further sanctions if it remains resistant to international demands.


Obama also sought to shore up support from world leaders for the war in Afghanistan, where U.S. combat deaths have risen as a resurgent Taliban has confounded efforts to stabilize the country.

The Obama administration is locked in an internal debate over whether to send more U.S. troops despite the American public's flagging support for the war and resistance from some of his fellow Democrats. NATO allies also have been reluctant to commit more forces to the 8-year-old war.

We have set a clear and focused goal: to work with all members of this body to disrupt, dismantle and defeat al Qaeda and its extremist allies, Obama said as he reasserted a U.S. commitment not to allow al Qaeda to use Afghanistan and neighboring Pakistan as safe havens for launching attacks.

Obama also used his speech to revisit his three-way talks on Tuesday with Israeli and Palestinian leaders, saying, The time has come to relaunch negotiations, without preconditions. The meeting yielded no breakthroughs on an issue he has set as a top priority for his administration.

Again showing impatience with the resistance of both sides to budge from entrenched positions, Obama said, All of us must decide whether we are serious about peace, or whether we only lend it lip service.

Sharpening his language from the previous day's session, Obama said, We continue to emphasize that America does not accept the legitimacy of continued Israeli settlements.
Israeli officials had put a positive spin on Obama's comments from the day before when he called only for restraint in settlement activity, after previously having demanded a total freeze on building on occupied land. Israel's right-leaning government has refused a complete halt.

But Obama also addressed one of Israel's chief complaints with outright condemnation of U.N. member states that launch vitriolic attacks on Israel's legitimacy. He was alluding to Iranian President Mahmoud Ahmadinejad, who frequently has questioned Israel's right to exist and denied the Holocaust.

(Editing by Will Dunham)