US Defense Secretary Leon Panetta warned Americans not to forget the troops who are fighting and dying in Afghanistan, as he paid tribute to the victims of the 9/11 attacks on Monday.
In a visit to a memorial in southwestern Pennsylvania honoring the passengers and crew of United Flight 93 that was hijacked on September 11, 2001, Panetta said the fight against the Al-Qaeda militants behind the attacks was not over, and that soldiers were still in harm's way.
"I pray that as we remember 9/11, and the terrible things that took place on 9/11, that we will also take the time to remind ourselves of the sacrifices that have been made by those who have fought and died in order to make sure that it not happen again," Panetta told reporters.
"My concern is that too often we do not express our concern and our attention to those who are fighting and dying for this country. We're continuing to lose good men and women in battle in Afghanistan," he said.
He drew a connection between the passengers of Flight 93, who struggled with their hijackers and foiled an apparent attempt by Al-Qaeda to strike Washington, and US troops waging war against Taliban insurgents eleven years later in Afghanistan.
The US soldiers are "putting their lives on the line every day," he said.
"That kind of sacrifice, that kind of commitment, that kind of dedication, that kind of courage is what makes this country strong.
"And we had damn well better remember that every day."
Panetta's impassioned plea to honor the more than 2,000 American troops killed in Afghanistan and the roughly 77,000 forces deployed there came amid a US presidential campaign that has barely touched on the conflict or foreign policy.
The war in Afghanistan, launched after the 9/11 attacks over the Taliban's alliance with Al-Qaeda, has steadily lost popular support but has generated no massive street protests or bitter debate similar to the one surrounding the Iraq conflict.
A growing majority of Americans oppose the US military presence there and support NATO's plan to withdraw most combat forces by the end of 2014.
The conflict rarely makes front page news, despite a steady flow of casualties and a vast investment in manpower and money, with political debate focused on how to revive the country's economy.
Panetta's trip to the memorial is the first in a series of anniversary ceremonies marking the 9/11 attacks which will unfold on Tuesday.
Events are scheduled in New York City, the Pentagon in Washington, and again in the rolling countryside in Pennsylvania at the crash site of Flight 93.
The Pentagon chief on Monday placed a wreath and bowed his head before marble slabs bearing the names of the 40 passengers and crew who died that day.
He then met with family members of the victims from the hijacked plane and walked to a boulder that marks the point where Flight 93 slammed into the ground in a ball of flame.
Eleven years ago, Flight 93 took off from Newark, New Jersey headed for San Francisco but was hijacked 46 minutes into the flight and ordered to turn towards Washington and its apparent target, the Capitol building.
From phone calls to loved ones on the ground, those on board learned that other airliners had been hijacked and used to attack the World Trade Center.
The passengers and crew voted to challenge the hijackers, and recordings from the plane captured the sounds of a struggle. The Boeing 757 crashed at full speed at 10:03 am, only 20 minutes flying time from Washington.
Panetta said that those aboard the aircraft had displayed "selflessness, determination and tremendous courage" that continues to serve as a source of inspiration.
"This is hallowed ground, because this is the final resting place of American patriots," he said.
Panetta, who as CIA director presided over the successful effort to track down and kill Al-Qaeda chief Osama bin Laden in May 2011, said the extremist network had been severely weakened but that there would be no let-up in Washington's campaign.
"We've decimated some of the very key leadership in Al-Qaeda. There is no question in my mind that we have impacted on their command and control and capability to be able to plan similar 9/11 attacks on this country," he said.
"But having said that, Al Qaeda terrorism still remains a threat, and it's for that reason that we are continuing to pursue them, in Yemen, and in Somalia, and in North Africa, and elsewhere."