WASHINGTON - President Obama is breaking with the go-it-alone Bush years in a new strategy for keeping the nation safe, counting more on U.S. allies to tackle terrorism and other global problems. It is an approach that already has proved tricky in practice.

The administration's National Security Strategy, a summary of which was obtained Wednesday, also for the first time adds homegrown terrorism to the familiar menu of threats facing the nation - international terror, nuclear-weapons proliferation, economic instability, global climate change, and an erosion of democratic freedoms abroad.

From mustering NATO forces for Afghanistan to corralling support to pressure North Korea to give up its nuclear-weapons program, the United States has sometimes struggled in leaning on friends and allies in recent years. Still, the new strategy breaks with some previous administrations in putting heavy emphasis on the value of global cooperation, developing wider security partnerships and helping other nations provide for their own defense.

In his first 16 months in office, Obama has pursued a strategy of gentle persuasion, sometimes summarized as "engagement." His administration has attended more closely to ties with Europe, sought a "reset" of relations with Russia, pushed harder to restart stalled Mideast peace talks, and consulted widely on a road map for defeating the Taliban in Afghanistan.

Presidents use their national security strategy to set broad goals and priorities for keeping Americans safe. But the document is not an academic exercise: It has far-reaching effects on spending, defense policies, and security strategy.

For example, President George W. Bush's 2002 strategy document spelled out a doctrine of preemptive war. "We must be prepared to stop rogue states and their terrorist clients before they are able to threaten or use weapons of mass destruction against the United States and our allies and friends," the Bush strategy said, with Iraq clearly in mind.

Obama's new strategy is expected to repudiate, at least implicitly, that doctrine.

John Brennan, the White House's top counterterrorism adviser, said Wednesday that adding the strategy of combating homegrown terrorism was a key element.

Attacks like the shooting at Fort Hood, Texas, last year, which killed 13 bystanders, as well as the failed Times Square bombing on May 1, have thrust homegrown terrorism into the spotlight, and U.S. citizens like Najibullah Zazi and David Headley have been charged with plotting terror attacks.

Brennan, speaking at the Center for Strategic and International Studies, did not disclose specifics of Obama's strategy paper. But he hinted at its philosophical underpinnings. Denouncing al-Qaeda as "a small band of cowards," Brennan said the United States would defeat the terror network while maintaining "our values as a nation."

Obama's document enshrines principles and policies that he has advocated since his election campaign. It will be the foundation for a National Military Strategy document, due soon. The strategy also makes clear the United States intends to maintain the world's most powerful military, with unsurpassed reach and capability despite being stretched by two wars and other challenges.

Obama touched on many of the themes in the new strategy during a commencement address Saturday to cadets at the U.S. Military Academy at West Point, N.Y.

The United States must shape a world order relying as much on the persuasiveness of its diplomacy as the might of its military, he said. All hands are required to solve the world's newest threats: terrorism, the spread of nuclear weapons, climate change, and feeding and caring for a growing world population, he added.