United States mourns on 15th anniversary of 9/11 terror attacks

America commemorated the 15th anniversary of the 9/11 attacks on Sunday with emotional services of remembrance in New York, Washington and Pennsylvania to honour those who perished in the world's deadliest terror strikes.

On 11 September, 2001, 19 al-Qaeda operatives crashed four passenger jets into the Twin Towers in Manhattan, the Pentagon and a field in Shanksville, Pennsylvania - killing almost 3,000 people and changing the world forever.

This year's anniversary comes with the US locked in a bruising White House election battle between Hillary Clinton and Donald Trump, who both attended the New York service, although Clinton left early after feeling unwell.

Even 15 years later, the long shadow cast by the attacks lives on in wars being fought today in Iraq and Afghanistan, and conflict tearing apart countries from Libya to Syria, allowing al-Qaeda affiliates and the Islamic State (IS) group to breed and prosper.

President Barack Obama said no words or deeds could ever truly erase the pain of loss, but urged Americans to stand true to the nation's ideals and not allow groups like al-Qaeda and IS to divide the country.

In remarks at the Pentagon, Obama praised the military and paid homage to those who lost their lives in New York, Washington and Pennsylvania that day. But his remarks also carried a more pointedly political message, the Washington Post said.

At a time when Trump has called for a ban on Muslims entering the US, Obama outlined a contrasting vision, the Post said. He offered a different definition of American strength.

Obama urged Americans to view the anniversary of the attacks as an opportunity to “reaffirm our character as a nation” and in what could be interpreted as a veiled reference to Trump’s immigration proposals, “not to let others divide us,” the Post said.

“In the end, the most enduring memorial to those we lost is ensuring the America we continue to be,” Obama said. “That we stay true to ourselves. That we stay true to what’s best in us.”
Obama described an America made up of “people drawn from every corner of the world, every colour, every religion every background,” the Washington Post reported.

“We know that our diversity, our patchwork heritage is not a weakness,” Obama said. “This is the America that was attacked that September morning.”

Emotion at Ground Zero

In New York, relatives fought back tears, clasped onto each other and bowed their heads at the 11 September Memorial on the site of the destroyed World Trade Center, which was closed to the general public.

The emotional service - in the shadow of the newly built Freedom Tower - observed six moments of silence to honour the four attacks and the moments each of the Twin Towers collapsed.

Each year, family members spend hours reading out the names of all the dead at the memorial, an increasing number of them young adults who never or barely knew lost parents, uncles, aunts and grandparents.

Mourners sobbed and laid flowers in the grooves of their loved ones' names, carved into the walls of two reflecting pools in the footprint of the towers overlooked by the Freedom Tower, the tallest building in the Western Hemisphere.

And New York Governor Andrew Cuomo announced plans for a new monument in the Big Apple to honour the first responders and survivors.

Lone-wolf threat

The US government says the country is now better protected against a 9/11-style terror attack, but the new threat is the lone-wolf assailant.

"Our government has become pretty good at detecting something hatched from overseas," Homeland Secretary Jeh Johnson told Fox News.

"Where we're challenged, however, is with the lone-wolf style attack, the self-radicalised actor. Terrorist organisations have the ability to [get] into our homeland through the internet and recruit and inspire."

The US, but more increasingly Europe, have been hit by such attacks, including the 2013 Boston Marathon bombings and the 2015 San Bernardino killings in California.

CIA chief John Brennan said the terror threat is diminished compared to 2001, including from the IS group, which he said is on the wane.

"It is now a failing organisation," Brennan said, speaking to CBS television's "Face the Nation" program.

Clinton, Trump on 9/11

"We'll never forget the horror of September 11, 2001. Today, let's honour the lives and tremendous spirit of the victims and responders," tweeted Clinton, who was a US senator from New York at the time of the attacks.

The former first lady left the ceremony at Ground Zero after becoming faint from the heat, according to her aides, as video footage showed her being helped, knees buckling, into her van by secret service agents.

She was taken to her daughter's Manhattan apartment to recover and emerged a couple of hours later feeling "much better," according to her campaign.

Her doctor later said Clinton was suffering from pneumonia and was overheated and dehydrated when she left the memorial.

Trump, meanwhile, called the anniversary "a day of sadness and remembrance," but also "a day of resolve".

It was the country's "solemn duty," he said in a statement, "to work together as one nation to keep all of our people safe from an enemy that seeks nothing less than to destroy our way of life."

George W Bush, who was president at the time of the attacks, spent the morning at church in Dallas, Texas, his home state.

He was due to attend the Dallas Cowboys home opener against the New York Giants, where he will take part in the ceremonial coin toss with NYPD officers who were at Ground Zero on 9/11.

Sunday marks the start of the NFL season in the United States, and those attending the American football games and watching on television will watch video messages from both Obama and Bush.

Some players in the predominately African American NFL joined US first responders and military personnel in pre-game tributes. 

But a protest over racial inequality and police brutality launched a few weeks ago by San Francisco 49ers player Colin Kaepernick has spread to other teams, including the Seattle Seahawks, with several players planning to link arms during the national anthem in a game that starts later Sunday.

Players on the Kansas City Chiefs also linked arms in unity, including one who raised a clenched fist Sunday during "The Star-Spangled Banner."