President Donald Trump and his Democratic rival Joe Biden held dueling commemorations Friday for the September 11, 2001 terror attacks on the United States, a bid to appear as leaders in a deeply divided national moment.

On the 19th anniversary of the Al-Qaeda attacks the former vice president Biden -- who has stepped up his campaign after keeping a low profile in light of the pandemic -- began the day in Manhattan for an annual event honoring the nearly 3,000 people who died in the destruction of the World Trade Center.

Trump did not attend the ceremony in his native New York, instead sending Mike Pence as a White House representative. Biden and the vice president tapped elbows and chatted briefly.

Neither would give official remarks, as the Ground Zero ceremony's speeches -- pre-recorded this year due to coronavirus measures -- are generally reserved for family members of victims.

But Biden's mere presence attracted attention at an event broadcast live on main US television networks and punctuated by minutes of silence, the first one at 8:46 am (1246 GMT), the time the first plane hit one of the Twin Towers.

The Republican president meanwhile travelled to Shanksville, Pennsylvania some 300 miles (480 kilometers) to the west of New York, where an airliner crashed after the passengers tried to wrest control from the Al-Qaeda hijackers.

The president and First Lady Melania Trump listened in silence as the names of the 40 passengers and crew killed aboard Flight 93 were read out -- with two bells tolling after the reading of each one.

Later in the day the Democratic presidential hopeful also will travel to Shanksville -- but there was no chance of the rivals crossing paths: Trump was due to leave well before Biden and his wife Jill arrive at the site.

'Scoring points'

Neither of these appearances are expected to feature political showmanship according to Robert Shapiro, a political scientist at Columbia University. The 9/11 ceremonies are traditionally "free of rhetoric, dedicated to paying tribute to victims" of the attacks, he said.

The ceremonies will nevertheless be closely followed by the media, and offer Biden and Trump a chance to "show their leadership and empathy."

"There will be a temporary silencing of the more vitriolic rhetoric they are using against each other," Shapiro said.

The choice of both candidates to show up in Pennsylvania, an important state to win in the presidential election, illustrates the "obvious calculations" their advisors have made.

Long a Democratic stronghold and Biden's home state, Pennsylvania swung narrowly to Trump in the 2016 election, helping him secure his surprise victory over Democrat Hillary Clinton.

Polls show Trump and Biden nearly even in Pennsylvania, and Democrats hope to win the state back in the November 3 vote.

But if the somber commemorations mark a "truce," it is likely to be a short-lived one, as was the case in 2016.

Clinton took part in the New York memorial but left the event early because she was feeling ill. Her doctor later revealed he had diagnosed her two days earlier with pneumonia, which she had kept secret.

Trump leaped on the incident and for weeks mercilessly mocked his rival's health.