美国纪念9-11恐怖袭击11周年

U.S. President Barack Obama and his wife Michelle will lead a moment of silence on the White House lawn Tuesday to mark the 11th anniversary of the al Qaida terrorist attacks on New York and Washington, D.C.

The Obamas will observe the event at the moment the first of two jetliners struck the World Trade Center in New York City, then will lead a similar ceremony at the memorial at the Pentagon, the headquarters of the U.S. military that was struck by a third plane in the 2001 attacks.

As in past years, the families of those killed at the World Trade Center will take part in a ritual reading of the victim's names at Ground Zero. But in a departure from previous observances, no elected official will take part in the Ground Zero ceremonies.

Vice President Joe Biden will speak at a ceremony in Shanksville, Pennsylvania where a fourth hijacked jetliner crashed after passengers tried to take control of the plane, preventing it from possibly reaching another target in Washington.