NEW YORK (AP) — Americans are commemorating 9/11 with tributes that have been altered by coronavirus precautions and woven into the presidential campaign, drawing both President Donald Trump and Democratic challenger Joe Biden to pay respects at the same memorial without crossing paths.

In New York, a dispute over coronavirus-safety precautions is leading to split-screen remembrances Friday, one at the Sept. 11 memorial plaza at the World Trade Center and another on a nearby corner. The Pentagon's observance will be so restricted that not even victims' families can attend, though small groups can visit the memorial there later in the day.

Trump and Biden are both headed — at different times — to the Flight 93 National Memorial near Shanksville, Pennsylvania.

Trump is speaking at the morning ceremony, the White House said. Biden plans to pay respects there in the afternoon after attending the observance at the 9/11 memorial in New York.

Meanwhile, Vice President Mike Pence is also due at ground zero — and then at the alternate ceremony a few blocks away.

In short, the anniversary of 9/11 is a complicated occasion in a maelstrom of a year, as the U.S. grapples with a health crisis, searches its soul over racial injustice and prepares to choose a leader to chart a path forward.

Still, 9/11 families say it's important for the nation to pause and remember the hijacked-plane attacks that killed nearly 3,000 people at the trade center, at the Pentagon and near Shanksville on Sept. 11, 2001, shaping American policy, perceptions of safety and daily life in places from airports to office buildings.

“I know that the heart of America beats on 9/11 and, of course, thinks about that tragic day. I don’t think that people forget,” says Anthoula Katsimatides, who lost her brother John and is now on the board of the National Sept. 11 Memorial & Museum.

Friday will mark Trump's second time observing the 9/11 anniversary at the Flight 93 memorial, where he made remarks in 2018. Biden spoke at the memorial’s dedication in 2011, when he was vice president.

The ground zero ceremony in New York has a longstanding custom of not allowing politicians to speak, though they can attend. Biden did so as vice president in 2010, and Trump as a candidate in 2016.

Though the candidates will be focused on the commemorations, the political significance of their focus on Shanksville is hard to ignore: Pennsylvania is a must-win state for both. Trump won it by less than a percentage point in 2016.

Around the country, some communities have canceled 9/11 commemorations because of the pandemic, while others are going ahead, sometimes with modifications.

The New York memorial is changing one of its ceremony's central traditions: having relatives read the names of the dead, often adding poignant tributes.

Thousands of family members are still invited. But they'll hear a recording of the names from speakers spread around the vast plaza, a plan that memorial leaders felt would avoid close contact at a stage but still allow families to remember their loved ones at the place where they died.

But some victims' relatives felt the change robbed the observance of its emotional impact. A different 9/11-related group, the Stephen Siller Tunnel to Towers Foundation, set up its own, simultaneous ceremony a few blocks away, saying there's no reason that people can't recite names while keeping a safe distance.

The two organizations also tussled over the Tribute in Light, a pair of powerful beams that shine into the night sky near the trade center and evoke its fallen twin towers. The 9/11 memorial initially canceled the display, citing virus-safety concerns for the installation crew. After the Tunnel to Towers Foundation vowed to put up the lights instead, the memorial changed course with help from its chairman, former Mayor Mike Bloomberg, and Gov. Andrew Cuomo.

Tunnel to Towers, meanwhile, arranged to display single beams for the first time at the Shanksville memorial and the Pentagon.

Over the years, the anniversary also has become a day for volunteering. Because of the pandemic, the 9/11 National Day of Service and Remembrance organization is encouraging people this year to make donations or take other actions that can be accomplished at home.

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Associated Press writers Alexandra Jaffe in Wilmington, Delaware, and Darlene Superville in Washington contributed.