Washington: Thousands will gather on Tuesday in New York, suburban Washington and rural Pennsylvania to mark the 11th anniversary of the Sept. 11 attacks, but at the somber day's biggest venue, Ground Zero in lower Manhattan, this year's observance will be missing a key feature from years past: politicians' voices.

In previous years, politicians including U.S. presidents, state governors and New York City mayors have participated in the reading of the names, or have read from the Bible or recited passages from literature.

This year, only the families of the more than 2,750 who were killed when militant Islamist hijackers crashed two jetliners into the World Trade Center's Twin Towers, causing their collapse, will appear on the podium to read their names.

Politicians may still attend, but under event rules set down in July by the National September 11 Memorial and Museum, chaired by New York Mayor Michael Bloomberg, none may speak or participate in the reading of names. Homeland Security Secretary Janet Napolitano will attend the New York ceremony this year.

The restrictions will not extend to politicians at the other remembrances, however.

At the Pentagon outside of Washington, where more than 180 were killed when a hijacked plane was flown into it, Defense Secretary Leon Panetta will speak in a ceremony that will be closed to the public, attended only by victims' families.

Vice President Joe Biden will deliver remarks in Shanksville, Pennsylvania, where 40 passengers aboard United Flight 93 were killed when that plane crashed as they revolted against their hijackers.

"How we handle the legacy of these 40 people and what they did, what they kept from happening, is really more of a statement about ourselves, about what we value as a society," said Patrick White, current president of Families of Flight 93. White's cousin, Joey Nacke II, was among the passengers who stormed the cockpit.

U.S. authorities say the al Qaeda hijackers planned to crash that plane into the U.S. Capitol in Washington.

Like so many of the previous anniversary dates, this year's ceremonies promise to unfold beneath blue skies and cool, early fall temperatures, conditions reminiscent of those on the morning of the 2001 attacks that claimed nearly 3,000 lives at the three sites.

In New York, there will be moments of silence to signal the times of impact of each plane: at 8:46 a.m, 9:03 a.m., 9:37 a.m. and 10:03 a.m.

Additional silences will be observed at 9:59 a.m. and 10:28 a.m., when the South and North Towers fell.

President Barack Obama and his wife Michelle will participate in a moment of silence on the White House lawn and then attend the Pentagon Ceremony, the White House announced last week.

In Shanksville, the names of 40 crew members and passengers aboard the plane will be read beginning at 10:03 by victims' families and local volunteers who assisted in the aftermath of the attacks. A bell will ring for the name of each of the 40 victims, and a wreath will be laid at the Wall of Names honoring the dead.

Secretary of the Interior Ken Salazar and White will also deliver remarks, the Parks Service said.

(Agencies)

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