New York, Sep 11 (Agencies): A day of mourning for nearly 3,000 September 11 victims began with moments of silence and tears near ground zero, as observers braced for protests over a mosque planned blocks away on what is usually an anniversary free of politics.

Chants of thousands of sign-waving protesters both for and against the Islamic center were expected after an annual observance normally known for a sad litany of families reading names of loved ones lost in the 2001 terrorist attacks.

Speaking at "hallowed ground" at the Pentagon, President Barack Obama alluded to the controversy over the mosque - and a Florida pastor's threat, later rescinded, to burn copies of the Muslim holy book. Obama made it clear that the US is not at war with Islam and called the al-Qaida attackers as "a sorry band of men" who perverted religion.

"We will not give in to their hatred," Obama said. "As Americans, we will not or ever be at war with Islam."

Family members gathering at observances in New York and Pennsylvania brought flowers, pictures of loved ones and American flags, but no signs of opposition or support for the mosque. Reading victims' names at ground zero in New York, they urged a restrained tone.

"Let today never, ever be a national holiday. Let it not be a celebration," said Karen Carroll, who lost her brother, firefighter Thomas Kuveikis. "It's a day to be somber; it's a day to reflect on all those thousands of people that died for us in the United States."

Standing before microphones, stifling sobs, some family members who read names sought to emphasize sentiments on all sides of the mosque argument.

Some - including Nadine DeGrange, whose uncle, Frank Wisniewski, 54, was killed - stressed that ground zero is hallowed.

"I come here every year because this is the only burial ground I know. And I pray to God it remains sacred," she said.

Others sought to embrace unity and a spirit of reaching out, which is what the developers of the Islamic center have said is their goal.

"May we share your courage as we build bridges with other people to prevent this from happening again and to preserve human dignity for all," said Robert Ferris, saluting the dozens of building workers who joined families in reading names.

Ferris lost his father, who worked at Aon Corp. Bagpipes and drums played to open the ceremony, followed by brief comments by Mayor Michael Bloomberg.

"Once again we meet to commemorate the day we have come to call 9/11. We have returned to this sacred site to join our hearts together, the names of those we loved and lost," Bloomberg said. "No other public tragedy has cut our city so deeply. No other place is as filled with our compassion, our love and our solidarity."

Moments of silence were held to mark the times the hijacked jetliners hit the north and south towers of the World Trade Center, as well as the times the towers collapsed. President Obama and first lady Michelle Obama attended separate services at the Pentagon in Washington and a rural field in Shanksville, Pennsylvania.

The mosque debate pits advocates of religious freedom against critics who say putting an Islamic center so close to ground zero disrespects the dead. While the rallies planned in New York embroiled victims' family members in a feud over whether to play politics, a threat to burn copies of the Quran was apparently called off.

Terry Jones, the Florida pastor who made the threat, flew to New York on Friday night and appeared Saturday on NBC's "Today" show. He said his church would not burn the Quran, a plan that inflamed much of the Muslim world and drew a stern rebuke from Obama.

"We feel that God is telling us to stop," he told NBC. Pressed on whether his church would ever burn the Islamic holy book, he said: "Not today, not ever. We're not going to go back and do it. It is totally canceled."

He said that he flew to New York in the hopes of meeting with leaders of the Islamic center but that no such meeting was scheduled.

Imam Feisal Abdul Rauf, leader of the planned mosque, said Friday that he was "prepared to consider meeting with anyone who is seriously committed to pursuing peace" but had no meeting planned with Jones.

Lending credence to Jones' comments, a "Burn a Koran Day" banner outside his Gainesville, Florida, church was taken down.

There was no immediate reaction to Jones' comments in Afghanistan, where on Saturday shops and police checkpoints had been set afire as thousands of people protested the planned burning 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 store 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."

Four red, white and blue balloons rose early Saturday from a public telephone booth near the building. Police cars lined the blocked-off street in front of the building.

Rosario Piedrahita, arriving with a bouquet of flowers and a photograph of her nephew, victim Wilder Alfredo Gomez, said she opposed using the site for a mosque.

"I say it's not good," she said. "It's like people standing up to celebrate after a victory."

John Bolton, who was US 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, along with 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 closed Saturday, the official end of the holy month of Ramadan. Police planned 24-hour patrols until next week. Worshippers on Friday were redirected to a different prayer room 10 blocks away.

In Shanksville, Michelle Obama and former first lady Laura Bush spoke to hundreds of people gathered at a memorial service for the 40 victims of Flight 93, which crashed about 60 miles (100 kilometers) southwest of Pittsburgh.

Flight 93 was en route from Newark, New Jersey, to San Francisco on Sept. 11, 2001, when hijackers seized control. But passengers fought back and the hijackers responded by crashing the plane.

Vice President Joe Biden spoke at the New York ceremony, where 2,752 people were killed when two jetliners flew into the trade center. Bells tolled to mark the times that each tower collapsed.