Victims' relatives, survivors and rescuers have observed the 16th anniversary of the September 11 terrorist attacks at ground zero in New York City.
Monday's commemoration began with a moment of silence and tolling bells at 8.46am (10.46pm AEST), which is the time when a terrorist-piloted plane slammed into the World Trade Center's north tower.
Then victims' relatives began reading the names of the nearly 3,000 people killed when four hijacked planes hit the centre, the Pentagon and a Pennsylvania field on September 11, 2001.
Republican President Donald Trump, a native New Yorker, is observing a moment of silence at the White House then taking part in an observance at the Pentagon.
It is his first time observing the anniversary as president.
There is also a ceremony at the Flight 93 National Memorial near Shanksville, Pennsylvania.
