The commemorative ceremony for the nearly 3,000 people killed by terrorists nine years ago began Saturday with a minute of silence at 8:46 am, marking the exact time when a hijacked commercial airplane struck one of the World Trade Center's twin towers in Lower Manhattan, dpa reported.
Government officials, headed by US Vice President Joe Biden, New York leaders and families of the victims met at the site to begin the solemn ceremony, following a familiar programme that began after the September 11, 2001 attacks.
New York City deployed hundreds of police in Lower Manhattan to handle demonstrators planning to protest against a mosque that a Muslim group wants to build two blocks from Ground Zero.
"We have a significant number of police to make sure that it is peaceful," New York Police Commissioner Ray Kelly said.
Terry Jones, the pastor who created a fury of world protests because of his plan to burn a Koran on Saturday, was in New York to try to meet with the Imam of the mosque near the World Trade Center.
Jones said he had decided not to burn the Koran.
"Most people don't want the mosque near Ground Zero and most people don't want the Koran to be burned," Jones said.
"We have a common denominator," he said. He arrived in New York late Friday and was given police protection.