WASHINGTON -- The nation observes its first Sept. 11, 2001, commemoration Friday with a new president, but continues to grapple with the best response to attacks that changed the global dynamic and remain embedded in the national psyche.

Americans stand divided over the U.S. approach to national security. U.S. troops fight an ongoing and increasingly difficult war in Afghanistan against an amorphous enemy while President Obama tries to reset the nation's image in the world.   

Public sentiment toward U.S. involvement in Afghanistan is souring as combat deaths grow and questions persist about flawed Afghan elections. The drawdown of U.S. troops in Iraq is moving forward though fears persist about Iraq's stability should it fall under the influence of declared enemies of the United States

Defense Secretary Robert Gates speaks of "a certain war-weariness on the part of the American people."

Sticky questions persist about what parts of former President Bush's anti-terror program to keep; what parts to throw away; what parts to investigate.

President Obama's goal of shutting the detention facility at Guantanamo Bay in Cuba within a year is bogged down in case-by-case complexities. A pledge to close the facility by January 2010 appears increasingly unlikely to be met.

The phrase "War on Terror" has fallen out of favor. Obama avoids using it, he says, to keep from offending Muslims.

Still, targeted strikes against Al Qaeda and Taliban leaders have resulted in the elimination of 11 top terrorists in the past year.

Keeping Americans safe, the president says, is "the first thing I think about when I wake up in the morning; it's the last thing that I think about when I go to sleep at night."

Bush used to say the same thing. On Friday, the former president issued a statement offering his respects to the victims and their families and to the all-volunteer Armed Forces, law enforcement and intelligence communities. 

"Their courage, service, and sacrifice is a fitting tribute to all those who gave their lives on September 11, 2001. On this day, let us renew our determination to prevent evil from returning to our shores," he said.

Eight years ago, Bush shouted into a megaphone at Ground Zero, the pit where the World Trade Centers had stood. He pledged to "rid the world of evil" and framed the worst act of terrorism on American soil with a black-and-white clarity that belied the complex challenges that lay ahead.

To weary rescue workers and a sorrowing nation, Bush declared: "The world hears you, and the people who knocked these buildings down will hear all of us soon."

Keeping America safe from another attack was a pledge the former president kept while in office despite bitter recrimination about the war in Iraq and whether it was the right battlefield. At home, Bush was accused of trashing the liberties of both Americans and terrorists detained in the military prison.

Obama has focused the war back to perilous Afghanistan, where terror groups have been largely routed but insurgents continue to blow themselves up and take as many people as they can with them. He is struggling to craft a clear message in the face of difficult decisions about how best to protect Americans and amid growing doubts about his ability to do so.

An AP-GfK poll released this week finds the president's approval ratings for his handling of Afghanistan and Iraq slipping, and declining approval, as well, for his efforts to combat terrorism.

On Friday's anniversary, the White House marked a moment of silence at 8:46, the time when the first tower was hit. 

"We remember with reverence the lives we lost," Obama said in a speech at the Pentagon memorial to honor those who died there in the 2001 attacks, and meet with loved ones of the dead. 

"We read their name, we press their photos to our hearts," he continued. "On this day that marks their death, we recall the beauty and meaning of their lives." 

He issued a proclamation Thursday urging Americans to mark the anniversary with acts of community service. He also pledged to "apprehend all those who perpetrated these heinous crimes, seek justice for those who were killed, and defend against all threats to our national security."

The president's challenge, says former Bush foreign policy adviser Juan Zarate, is to "find a balance where he's clearly marking 9-11 as a key historic moment from which his current policies flow, but also not allowing it to define him," as the attacks defined Bush's presidency.

"The Bush administration was often viewed as too firmly planting its policies in 9-11 and in the War on Terror," said Zarate, now an adviser at the Center for Strategic and International Studies.

In the years since 2001, American worry more now about the economy, health care and unemployment than terrorism, polls show, and they elected a new president with high hopes that he would act decisively on those issues and with underlying expectations that he would keep them safe.

So Obama's challenge is to focus on terror even as he engages in a historic effort to restructure the nation's health care system and works to nurse the economy back to health.

There is spirited debate within the Obama White House over what to do next in Afghanistan, and whether to send in more troops to stop extremists and stabilize Pakistan.

The president says his goal is clear: to "disrupt, dismantle and defeat Al Qaeda and their extremist allies." The way to do that, he argues, is by fighting the insurgents in Afghanistan to prevent the country from again becoming a haven for Al Qaeda.

"But lots of people have not bought it," said Stephen Biddle, a fellow at the Council on Foreign Relations who has served as a civilian adviser to the general in charge of the U.S. war effort in Afghanistan. "Surely a big piece of the declining poll numbers for support for Afghanistan is that the public does not yet see the connection between Afghanistan and Al Qaeda today."

Peter Feaver, a Duke University expert on war and public opinion who worked in the Bush White House, said that mixed messages coming out of the White House are partly to blame for the public's confusion. The administration's talk about a narrow mission to fight terror did not jibe with its broader efforts to help rebuild the country and promote economic stability, he said.

The public, Feaver said, is uncertain "where the president's gut is on this issue.

Michael O'Hanlon, a foreign policy expert at the Brookings Institution, said it would be a mistake to measure Obama's success at fighting terrorism only by the yardsticks of Iraq and Afghanistan.

The president also is trying to promote security on the home front, working with partners in other countries and waging a broader battle to defuse hatred and extremism that fuel terrorism globally, he said.

Americans are pragmatic enough to evaluate those efforts case by case, says O'Hanlon, and "ultimately, the judge of whether we're making progress is whether we get attacked again."

The Associated Press contributed to this report.