(Adds quotes from New York ceremony)
By Victoria Cavaliere and Mark Felsenthal
NEW YORK/WASHINGTON, Sept 11 (Reuters) - Bagpipes, tolling bells and a reading of the names of the nearly 3,000 people who died when hijacked jetliners crashed into the World Trade Center, the Pentagon, and a Pennsylvania field marked the 12th anniversary of the Sept. 11 attacks in 2001.
More than a thousand people gathered Wednesday on a hot and hazy morning at the National September 11 Memorial plaza in Manhattan, for the annual reading of victims' names from both the 1993 and 2001 terror attacks on the World Trade Center.
Bagpipes and a youth choir opened the solemn proceedings, held around two memorial pools in the footprints of the twin towers on the 16-acre site of the former World Trade Center complex.
Many of those reading from the list of names directly addressed their own lost loved ones in emotional tributes.
"Cathy, your brothers and sisters still miss you. All the people whose lives you touched," said Eleanor Salter, whose daughter, Catherine Patricia Salter, perished. "As for me, life goes on. But it would have been really fun with you around. I miss your smile."
Gabriella Scibetta was only 4 years old, and her brother Vincent was a baby, when their mother, Adriane Victoria Scibetta, died in the South Tower.
"Vincent and I love and miss you, you'll never be forgotten," Scibetta said.
In keeping with a tradition begun last year, no public officials spoke at the New York ceremony, although former New York Mayor Rudolph Giuliani, his successor Michael Bloomberg, Police Commissioner Raymond Kelly, and other city and state leaders were in attendance.
In Washington's memorial service at the Pentagon, President Barack Obama called on Americans to pray for those whose lives had been lost.
"Let us have the strength to face the threats that endure, different though they may be from 12 years ago, so that as long as there are those who would strike our citizens, we will stand vigilant and defend our nation," Obama said.
The morning after a speech in which he urged Americans to support his proposal to use military force against Syria, in retribution for President Bashar al-Assad's poison gas attack on his own people, Obama also reflected on the limits of force.
"Let us have the wisdom to know that, while force is at times necessary, force alone cannot build the world we seek," Obama said.
Americans observed a moment of silence at 8:46 a.m. EDT (1246 GMT), the time American Airlines Flight 11 smashed into the North Tower and there was a second pause at 9:03 a.m. (1303 GMT) when United Airlines Flight 175 struck the South Tower.
More moments of silence came at 9:37 a.m. (1337 GMT), when American Airlines Flight 77 hit the Pentagon; at 9:59 a.m. (1359 GMT) when the South Tower collapsed; at 10:03 a.m. (1403 GMT) when United Flight 93 hit the ground near Shanksville, Pennsylvania; and at 10:28 a.m. (1428 GMT), when the North Tower fell.
Nineteen hijackers were killed in the suicide attacks, for which Osama bin Laden and al Qaeda claimed credit, leading to the U.S. war in Afghanistan and indirectly to the invasion of Iraq.
Twelve years later, two skyscrapers have been nearly completed on either side of the plaza, including One World Trade Center, the tallest building in the Western Hemisphere at a symbolic 1,776 feet (541 meters), a number chosen for the year of the U.S. Declaration of Independence.
At the Flight 93 National Memorial wall in Pennsylvania, the National Park Service's ceremony of remembrance on Wednesday included a reading of the names of the passengers and crew, a ringing of bells, a wreath-laying and tributes. (Reporting by Victoria Cavaliere in New York and Mark Felsenthal in Washington; Editing by Scott Malone, Bernadette Baum and Gunna Dickson)