NEW DELHI: On the 20th anniversary of the 9/11 attacks, US President Joe Biden defended America's troop pullout from Afghanistan asserting that there was no other way to have done it.

"If you had told anybody that we are going to spend $300 million a day for 20 years to try to unite the country after we got Bin Laden after Al Qaeda was wiped out there - could Al Qaeda come back? Yes. But guess what, it's already back in other places," the US president said.

Biden while paying tribute to victims of the fourth plane crash which crashed at Shanksville, Pennsylvania on 9/11 said that it wasn't feasible to invade and stay in all the places that Al Qaeda was present.

"Every place where Al Qaeda is, we're going to invade and have troops stay in? Come on. As I read it, I'm told 70 per cent of American people think it was time to get out of Afghanistan, spending all that money but the flip side of it is- they didn't like the way we got out but it's hard to explain to anybody - how else could you get out?"

Relatives of people who died on 9/11 have read out victims' names, many struggled to hold back tears at the ceremony held at Ground Zero, the site of the Twin Towers destroyed in the attacks by al-Qaeda militants.

A minute's silence was held at the exact time each hijacked plane crashed.
George W Bush, who was the US president at the time, gave a speech in Pennsylvania, where one of the planes crashed into a field after passengers overpowered the hijackers.

"The world was loud with carnage and sirens, and then quiet with missing voices that would never be heard again," he said. "It's hard to describe the mix of feelings we experienced."

The official memorial in New York started with a minute's silence at 08:46 (12:46 GMT) - the exact moment the first plane hit the North Tower of the World Trade Center in 2001.

All morning, roses continued to be placed beside the names of the 2,977 victims etched into the Ground Zero memorial.
There were five more moments of silence over the next few hours - marking the time when the second plane crashed into the South Tower, when a third jet struck the Pentagon just outside Washington DC, when the fourth plane crashed in Pennsylvania, and finally when each tower collapsed.
The tributes continued into the night, as two beams of light shone four miles (6.4 km) into the sky.