This 9/11 is more political and contentious than the eight before it, with grieving family members on opposite sides of the mosque battle.
The debate became so heated that President Obama felt the need to remind Americans: "We are not at war against Islam."
It was uncertain Friday whether hushed tones would replace the harsh rhetoric that threatened to overshadow the commemoration of the terrorist attacks that killed nearly 3,000 people in New York, Washington and Shanksville, Pa.
The son of an anti-Muslim minister in Florida confirmed that his father would not - at least for now - burn copies of the Quran (Koran), a plan that inflamed much of the Muslim world and drew a stern rebuke from Mr. Obama. But Terry Jones got on a plane and landed in New York on Friday night. Jones has said he wants to meet with the imam behind the proposed mosque.
Surrounded by a throng of police, Jones declined to comment to reporters who waited for him at LaGuardia Airport and followed him to a waiting cab.
"I'm talked out," he said.
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Activists in New York insisted their intentions were peaceful.
"It's a rally of remembrance for tens of thousands who lost loved ones that day," said Pamela Geller, a conservative blogger and host of the anti-mosque demonstration. "It's not a political event, it's a human rights event."
The site of the proposed mosque and Islamic center is already used for services, but it was padlocked Friday, closed until Sunday. Police guarded the block, and worshippers were redirected to a different prayer room 10 blocks away.
More than 2,000 supporters of the project, waving candles and American flags, held a vigil near the proposed Islamic center's site Friday evening instead of Saturday, saying they wanted to avoid entangling the mosque controversy and the Sept. 11 observance.
Organizers "believe that tomorrow is a day for mourning and remembrance," said Jennifer Carnig, a spokeswoman for the New York Civil Liberties Union, one of the vigil's sponsors.
Stephanie Parker, daughter of 9/11 victim Philip L. Parker of Skillman, N.J., said she came to the vigil because she's troubled by what she sees as people wrongly equating all of Islam with the extremists who attacked the trade center, and by the way the furor surrounding the mosque has become entangled with the attacks' anniversary. She has previously chosen to spend those anniversaries with her family.
"I think the anniversary is being overshadowed," Parker, 21, a senior public relations major at Drexel University in Philadelphia, said in an interview as she relighted a candle that kept blowing out in a breeze.
U.S. Rep. Keith Ellison of Minnesota called for devoting Sept. 11 to honoring victims and the first responders who worked to save them - not the Islamic center controversy.
"It is not proper or right to distract from honoring those heroes and remembering those victims. Not doing anything else than that tomorrow," Ellison, who is Muslim, told the crowd. "And yet we know the possibility of that is real."
For Jones, pastor of a 50-member Pentecostal church in Florida, it was to be a day to burn the Quran. He backed off that threat after drawing angry protests across the Muslim world, a call from the secretary of defense and impassioned pleas to call it off from religious and political leaders and his own daughter.
"There will be no Quran burning tomorrow," Jones' 29-year old son, Luke Jones, told reporters outside his father's Gainesville church Friday. He added that he could not predict what might happen in the future.
Terry Jones had previously said he would cancel his plan if the leader of the planned New York Islamic center, Imam Feisal Abdul Rauf, would agree to move the project to another location.
Jones claimed Thursday that an imam in Florida had told him the mosque would be moved. That imam later said Jones was mistaken, that he had only arranged a meeting with Rauf in New York on Saturday.
Rauf, however, said that wasn't true, either, that he had no plans to meet with Jones, although he added in a statement Friday that he is open to seeing anyone "seriously committed to pursuing peace."
The carefully worded text seemed to leave open the possibility of a meeting, but only if Jones proved himself to be a serious peacemaker. With that caveat, it would seem unlikely that the imam would meet with a man whose threat to desecrate the Muslim holy book stirred anger and protest and even some bloodshed in the Islamic world.
In Afghanistan, 11 people were injured Friday in scattered protests of Jones' plan. Only a few thousand people attended those rallies and no large-scale demonstrations were reported elsewhere. In Indonesia, the world's most populous Muslim country, cleric Rusli Hasbi told 1,000 worshippers at Friday prayers that whether or not Jones burns the Quran, he has already "hurt the heart of the Muslim world."
As on other 9/11 anniversaries, official ceremonies were planned at the three locations where the terrorists struck. Mr. Obama will be at the Pentagon, Vice President Joe Biden will go to New York, and first lady Michelle Obama and former first lady Laura Bush will travel to Shanksville.
Mr. Obama told a White House news conference that Sept. 11 would be "an excellent time" for the country to reflect on the fact that there are millions of Muslims who are American citizens, that they also are fighting in U.S. uniforms in Afghanistan, and "we don't differentiate between 'them' and 'us.' It's just 'us."'
Biden will attend the largest commemoration, at a park near ground zero, where 2,752 people were killed when Muslim extremists flew planes into the twin towers of the World Trade Center. Houses of worship in the city will toll bells at 8:46 a.m., when the first plane struck the north tower, and three more times to mark the moment the second plane hit the south tower and to observe the times each tower fell.
Activists are organizing a pair of rallies - one against the planned Islamic center, one supporting it - to follow the official ceremony.
Sally Regenhard, who lost her firefighter son, Christian Regenhard, planned to attend the morning ceremony and the anti-mosque protest.
"The purpose is to speak out and express our feelings that this mosque, the location of it, is a grievous offense to the sensitivity of 9/11 families," Regenhard said. "There's nothing political about people who want to speak out against something they think is so wrong, so hurtful and so devastating."
But Donna Marsh O'Connor, whose pregnant daughter, Vanessa, was killed in the attacks, supports the mosque. She said she strongly opposes the anti-mosque rally and the political motivations behind it.
"It's more of the same hate-mongering and fear-mongering that's been going on for years," O'Connor said. "People have a right to free speech. But if they're talking about sensitivities to 9/11 families, why are they rallying and doing events on a day we should spend thinking about those we lost?"
John Bolton, who was U.S. ambassador to the United Nations under President George W. Bush, was expected to send a videotaped message of support to the anti-mosque rally, as was conservative blogger Andrew Breitbart. Anti-Islam Dutch politician Geert Wilders, who advocates banning the Quran and taxing Muslim women who wear head scarves, plans to address the crowd in person, as do a handful of Republican congressional candidates who have made opposition to the mosque a centerpiece of their campaigns.
Also Saturday, former Republican vice presidential candidate Sarah Palin was expected to observe the anniversary in Alaska with Fox News TV host Glenn Beck.
New York Archbishop Timothy Dolan spoke out Friday against Saturday's planned New York protests, saying Sept. 11 "has become a holy day in our community and our nation."
"We must never allow Sept. 11th to become a time for protest and division," he added. "Instead, this day must remain a time for promoting peace and mutual respect."