Chants of thousands of sign-waving protesters both for and against the planned Islamic center were expected after - and perhaps during - a ceremony normally known for somber church bells ringing and a sad litany of families reading their lost loved ones' names.
President Barack Obama and first lady Michelle Obama were to attend separate services in Washington and Shanksville, Pa., for the victims of hijacked jetliners that hit the Pentagon and a rural field in 2001.
But the rallies planned in New York embroiled victims' family members in a feud over whether to play politics on the ninth anniversary of the attacks.
Nancy Nee, whose firefighter brother was killed at the World Trade Center, is bitterly opposed to the Park51 proposed mosque and Islamic community center near ground zero. But she didn't plan to join other family members at an anti-mosque rally hours after the anniversary ceremony.
"I just wanted to be as at peace with everything that's going on as I possibly can," Nee said. Even nine years later, she said, her brother George Cain's death "is still very raw. ... And I just don't have it in me to be protesting and arguing, with anger in my heart and in my head."
Jim Riches planned to pay respects at ground zero to his firefighter son, Jimmy, then rally.
"My son can't speak anymore. He's been murdered by Muslims. I intend to voice my opinion against the location of this mosque," Riches said. "If someone wants to go home, that's their right. I have the right to go there."
The heated mosque debate - pitting advocates of religious freedom against critics who say that locating an Islamic center so close to ground zero disrespects the dead - led Obama to remind Americans on Friday, "We are not at war against Islam."
A threat to burn copies of the Muslim holy book on the anniversary - which had set off international protests - was on hold, although the Florida pastor who made the threat flew to New York on Friday night, declining to comment to a throng of reporters waiting for him. "I'm talked out," Terry Jones said.
Jones' son in Gainesville, Fla., confirmed that his father would not - at least for now - burn copies of the Quran, a plan that inflamed much of the Muslim world and drew a stern rebuke from Obama.
Jones, pastor of a 50-member Pentecostal church, backed off the threat on Thursday after a call from the secretary of defense and impassioned pleas to call off the plan from religious and political leaders and his own daughter.
Jones previously had said he would cancel his plan if the leader of the proposed Islamic center, Imam Feisal Abdul Rauf, would agree to move the project to another location and had said he wanted to meet with Rauf in New York.
Rauf said Friday he was "prepared to consider meeting with anyone who is seriously committed to pursuing peace" but had no such meeting planned with Jones.
In Afghanistan, shops and police checkpoints were set in fire Saturday as thousands of people protested Jones' plan and chanted "Death to America" in Logar province. At least 11 people were injured Friday in similar protests in Badakhshan province.
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 already has "hurt the heart of the Muslim world."
Activists in New York insisted their intentions were peaceful. More than 1,000 protesters on both sides of the issue were expected to converge at the mosque site, a former clothing factory two blocks north of the trade center site.
"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."
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, planned 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.
Muslim prayer services are normally held at the site but it was padlocked Friday and would be closed Saturday, the official end of the holy month of Ramadan. Police planned 24-hour patrols of the site until next week. Worshippers on Friday were redirected to a different prayer room 10 blocks away.
While the president was at the Pentagon service Saturday and the first lady was to join former first lady Laura Bush at Shanksville, Vice President Joe Biden planned to speak at the New York ceremony, where 2,752 people were killed when two jetliners flew into the trade center. Bells were to toll for the first time at 8:46 a.m., the minute that the first plane struck the first tower, and then three more times to mark the moment the second plane hit the tower and for the times that each tower collapsed.
More than 2,000 supporters of the project, waving candles and American flags, held a vigil Friday night at the mosque site, saying they wanted to avoid entangling the mosque controversy and the Sept. 11 observance.
Stephanie Parker, whose father, Philip L. Parker, worked for an insurance company at the trade center, normally spends the attacks' anniversary privately with family. The mosque furor brought her out for the first time.
"I think the anniversary is being overshadowed," Parker, 21, said as she relighted a candle that kept blowing out in a breeze. "This year, I feel like I should use my voice and my position" as a victim's relative to speak up for tolerance, she said.