WEST POINT, N.Y. — Seeking to redefine America's foreign policy for a post-war era, President Barack Obama on Wednesday declared that the United States remains the only nation with the capacity to lead on the world stage but argued it would be a mistake to channel that power into unrestrained military adventures.

Obama's approach, outlined in a commencement address at the U.S. Military Academy, underscored his efforts to straddle the line between global isolation and intervention. Neither view, he said, "fully speaks to the demands of this moment."

"It is absolutely true that in the 21st century, American isolation is not an option," Obama said in remarks to more than 1,000 of the military's newest officers. "But to say that we have an interest in pursuing peace and freedom beyond our borders is not to say that every problem has a military solution."

Obama has often struggled to articulate not only what should fill the space between intervention and isolation but also any success the administration has had in finding that middle ground. His preferred tool kit, which includes economic sanctions, diplomatic negotiations and international coalition building, rarely generates quick fixes and is often more ambiguous than more easily explained military action.

The president's strategy also has garnered mixed results. While diplomacy and sanctions have brought the U.S. and Iran closer to a nuclear accord than ever before, neither approach has stopped the bloodshed of Syria's four-year civil war or prevented Russia from annexing territory from Ukraine.

The result at home has been a drumbeat of criticism from Republicans and others who say the president has squandered America's global leadership and emboldened international foes in Syria and Russia, as well as China. The public's approval of the president's foreign policy has declined, even as his policies hew closely with Americans' stated opposition to more military conflicts.

Obama's speech on Wednesday was part of concerted White House effort to answer critics and more clearly define his foreign policy philosophy. He outlined plans to seek approval from Congress for $5 billion that could be used to help countries fighting terrorism, foreshadowed a more robust U.S. military program to train and equip vetted Syrian rebels and declared that seeking international consensus through the United Nations or NATO is an example of American leadership, not weakness.

The president vigorously defended his belief that unilateral American military action should be reserved for instances where core national interests are challenged or the public's safety is in jeopardy.

He told the graduating cadets: "I would betray my duty to you, and to the country we love, if I sent you into harm's way simply because I saw a problem somewhere in the world that needed fixing, or because I was worried about critics who think military intervention is the only way for America to avoid looking weak."

Obama's speech came one day after he unveiled plans for ending the Afghan war by 2016, bringing to a close a conflict that started in the weeks after the Sept. 11, 2001, terror attacks. He was cheered by his commencement audience when he noted that the cadets had the distinction of being "the first class to graduate since 9/11 who may not be sent into combat in Iraq or Afghanistan."

Thirteen years after 9/11, Obama said terrorism remains the most direct threat to American security, though the risks of a massive attack on the homeland from a centralized al-Qaida have taken a backseat to more diffuse threats from an array of affiliate groups.

As the threat changes, so too must America's response, Obama said. Instead of large-scale military efforts, he called for partnering with countries where terrorist networks seek a foothold, including Yemen, Libya and Mali. In Afghanistan as well, the U.S. will put an emphasis on counterterrorism missions in the final two years of the U.S. mission.

Defense Secretary Chuck Hagel, in his first public comments about the troop drawdown plans outlined by Obama, said Wednesday there still were a lot of unanswered questions about how many of the nearly 10,000 U.S. personnel remaining in Afghanistan next year will be devoted to the counterterrorism mission. He said it also was unclear how many troops NATO and other international partners would contribute and what exactly those forces would do.

Hagel, who spoke to reporters traveling with him on a 12-day trip to Asia and Europe, expects to meet with NATO defense ministers next week. He said he also will be traveling to Afghanistan during this overseas trip.

In his speech, Obama also sought to cast Syria as more of a counterterrorism challenge than a humanitarian crisis. He defended his decision to keep the U.S. military out of a sectarian civil war and said the American response would focus on increasing assistance for the moderate opposition and helping neighboring countries including Jordan and Lebanon that have faced an influx of refugees and fear extremists spilling over their borders.

The Syria conflict perhaps more than any other illustrates the difficulties Obama faces in seeking to hit the sweet spot between isolation and intervention

He was among the first world leaders to call for the ouster of Syrian President Bashar Assad as the violence escalated, but economic sanctions and diplomatic negotiations failed to push the Syrian leader out of power. Obama appeared ready to launch a military strike last year after Assad's government used chemical weapons — a step that crossed Obama's self-proclaimed "red line" — but backed away, choosing to seek to seek congressional approval first, then scrapping a strike altogether in favor of an international agreement to strip Syria of its chemical weapons.

While the administration casts the chemical weapons accord as a success, it has done little to quell the violence that has left more than 160,000 people dead. Obama has approved some lethal aid to help bolster the Syrian rebels but has resisted sending the heavy weaponry they are seeking.

Even the new opposition training program he is considering comes with caveats. Officials said Obama would seek congressional approval for the plan, meaning it could be weeks or months before the assistance is finalized.

Rep. Ed Royce, R-Calif., chairman of the House Foreign Affairs Committee, welcomed the possibility of increased American attention to Syria but said it wouldn't change the fact that "the president has been late in responding to this crisis."