Eight years on, Obama to lead 9/11 tributes

President Barack Obama will lead tributes to the nearly 3,000 people killed on 11th September 2001 on the eighth anniversary of the devastating attacks on Friday.

Events were re-scheduled across the United States to remember the day when Americans watched in horror as four airliners hijacked by Al-Qaeda were flown into the World Trade Center towers in New York, the Defense Department headquarters near Washington and a Pennsylvania field.

Obama will pay tribute to the victims in a speech at the Pentagon, then meet relatives of those killed in the attacks. Vice President Joseph Biden will attend commemorative events in New York, the White House said.

The day of tributes begins in New York, where two jet airliners slammed into the Twin Towers, killing 2,752 people and prompting President George W Bush to declare a "war on terror". At the site where the towers once stood, relatives of those killed will join volunteers from across New York city to read the names of the victims.

The public reading, now an annual ritual, will be paused four times to mark the moments when American Airlines Flight 11 and United Airlines Flight 175 hit the buildings, and when the two towers collapsed. At nightfall, two beams of light will shoot skyward from the site.

Obama is to lead the tributes in Arlington, Virginia, where a third hijacked plane, American Airlines Flight 77, crashed into the Pentagon building. The president, accompanied by Defense Secretary Robert Gates and chairman of the Joint Chiefs of Staff Admiral Michael Mullen, is to observe a moment of silence, deliver a speech and lay a wreath.

He will then meet with relatives of the victims and tour a memorial to the 184 people killed on the ground and aboard Flight 77. The Pentagon memorial is the only major official monument to the victims of the 11th September attacks, with plans for similar sites in New York and Pennsylvania held up in part by financial and legal wrangling.

At the World Trade Center site, progress has been slow on the foundation of "Freedom Tower" -- part of a planned complex of five new skyscrapers, with a park and memorial in the middle.

With plans hampered by the financial crisis and the real estate downturn, the site just looks like a large hole, although work on foundations of several key elements is underway and the frame for the future tower is rising